Buckling in Self.

Mine are 6 and 4, and both now in regular booster seats, and both buckle themselves in now.
They couldn't do it in the harness style seat, but now that it's just the regular seat belt, it's no problem.
And man, it's awesome! I HATED strapping them into those seats so much.

It also depends on the straps. My DD can buckle the top part of her harness, but cannot get the bottom clip herself. Other children are in high backed boosters with a seatbelt and that is a different skill level. I agree that you should continue to assist til she shows you she can do it herself, all the time.

I think this has just so much to do with the personality of the child. My boys have always been the super, independent, "I do it myself" type. I never taught them how to buckle up, but they were buckling themselves in when they were 2 or 2 1/2 (it's been awhile, so I can't be sure).

I had no reason to try and stop my boys from buckling themselves in. If I had tried to stop them, they simply would have tried harder and been more insistent that they did not need my help. Nothing wrong with me double checking the straps when they were done :-)

One of my brother's girl, while having many wonderful gifts, does not possess the same independent streak my boys do. When she was 5 she had to be taught and encourage to unbuckle her own seatbelt (she was in a booster). I had to delay my boys transition to a booster for fear they would unbuckle while I was driving.

I don't think you're in a hurry to do this, but if she tries to buckle herself in I would definitely encourage her. I think you will naturally come to a point where you want her to be more independent. You'll be able to check what she's done to make sure there are no safety concerns.

Try not to worry too much about these things. Kids have different personalities, and some are going to want to learn certain skills much faster.

Until he was out of car seats and boosters - I did all the buckling where our son was concerned.
When he was about 7 yrs old he was fine doing it himself.
3 or 4 yr old can mess with buckles - they don't know what's safe - and too many of them unbuckle while the car is moving.
Never mind what other kids are doing - you keep yours safe.

I think it's important for you to continue to buckle her in. If she wants to buckle herself in teach her how to do that but continue to check what she's done.

I checked my grandchildren's seat belt until they were in grade school and I consistently found it fastened correctly. Preschoolers are too easily distracted.

Age 4 for both my kids. I love it...my daughter is 4.5 right now and it's so nice for me to not have to buckler her in. Yes, I check to make sure she did it right. Sometimes I have to adjust or tighten it.

My daughter has been able to buckle her own harness since she was somewhere between 3 and 4.

Just because they buckle themselves, doesn't mean you don't check their fit... Even now she is still in a harnessed booster and I check her buckle every time she gets in. If necessary I tell her to adjust the chest clip or pull the straps a little tighter - but she can do it herself.

Mine were a little over 2. My nephew didn't learn until he was 4 his mother babied him so much it made me nuts!!!!

Updated

Mine were a little over 2. My nephew didn't learn until he was 4 his mother babied him so much it made me nuts!!!!

My 4 year old buckles himself in (5-point harness), but I do a quick check of the placement of the top clip and I tighten the straps after he does so. It's handy at places like stores, where he can buckle in while I get groceries into the trunk. I do a quick check as I pass by his car door before I buckle myself in.

He cannot undo the clip or buckles himself.

My older son was the same, and wasn't completely independent until he moved to a booster.

My son is almost 3 and can buckle himself in, but I always check him those times he does.

I still buckle my youngest kiddo in (5) because the clasp the buckle clicks
into is hard to get to because of the car seat.
I would let her do it then check it.
Or just do it yourself to ensure she is safely buckled in.
She can assert her newfound, growing independence in other ways.
Better to be safe than sorry.

My kids did it pretty young, like around three, but at least in my case, they could also unbuckle themselves. Since I had to strike that fear of god in them it was simple to go over making sure it clicks.

The middle bit they had no trouble with but I did have to let out the straps as they grew.

Unless they have changed, my youngest is 13, the most important thing is getting that darn thing secured to the car. The click is easy to confirm and it either clicks or you have to check, easy.

My oldest around 4, my son around 3. Toddler, probably 3, super coordinated and physical.

I do check to see where the chest clip rests.

I actually think boosters are safer as they get older. They can do it all themselves, nothing is tangled, and everything sits where it should. We are in the process of moving to boosters. They have them in hubby's car, and some travel ones for when they go to my parents, but I need to take the car seats out of the van.

My daughter learned how to buckle herself in a 5-point harness when she was 4.5. Unbuckling took a little longer. A lot of kids learn to buckle earlier because a lot if parents keep the straps too loose or loosen them to facilitate the kids doing it themselves. When the straps are kept at the proper tightness, to where you can't pinch them together, it's a harder task to manage. My kids both learned to buckle their chest clips at 2 and to adjust them properly by 3, which is an easier feat when the bottom clips aren't done yet.
Keep up the safe carseat usage and your daughter will learn to buckle and unbuckle in time.

For the entire time we used a 5 point harness, we (the adults) checked the buckles. Age doesn't matter; a parent should always physically double check with a harness seat even when a kid can click it into place.

When we switched to high back boosters, the kids did it on their own. It was easy to hear/see that it was right without being hands-on.

My daughter started buckling herself right around the time she turned 3.5, maybe a month or so before. However, I still check it every time and make sure it is tight enough.

I always did the 5 point harness. When we moved to booster seats they started doing it on their own, but I still check that they have them pulled tight.

I think it's great to encourage kids' independence, but you don't have to be influenced by what you see other kids doing. As you point out, it's so incredibly dangerous if anything is done wrong. Once you show a child how to buckle, they automatically know how to UN-buckle. If they become really fascinated with the mechanism and the "look, I did it myself" philosophy, they may not be able to control themselves while you are driving. So you really have to know your kid, how good she is at following rules and observing safety precautions "just because Mom said so" and not because she's really old enough to internalize those values. If you think she may be quietly unbuckling without you hearing her, or if you won't be able to pull over right away even if you are aware of it, then no, it's too soon. But if she's very compliant and you think you can get her to do it right and keep it done now, before she gets into a defiant stage, then go ahead. But I'd still say "trust, but verify" and check her at all times. If you have any concerns, just encourage independence in a bunch of other areas. I don't think parents need to feel badly about being very vigilant about safety, whether that means holding a child's hand even if they usually stick right by your side and look both ways, or buckling them in, or checking to be sure they really aren't doing something on the computer that they aren't supposed to!

I am pretty sure I was still buckling my son into his 5 point harness when he was 5. Didn't see a reason to stop checking the straps every time - it takes 10 seconds - less time than it takes a kid to find and buckle themselves and then I knew it was done right.

It really depends upon the child. My oldest could do it by herself by 4. My youngest was way too spazzy to trust with it at that age. I always did it for her when she was in a 5-point harness (she would try to do it herself, but it didn't always click in all the way). When she was 6 and moved to a belt-positioning booster, she was able to competently do it by herself.

You know your child best - if she still needs help, don't rush this. Safety is too important.

My 8-year-old is in a 5 pt. harness and can do it himself. (He actually does it great; we've practiced a lot and I am very picky).

My 4-year-old just learned how, too.

You will likely have to adjust straps and chest clip, etc.

I do have a 6-year-old in a booster (that specific seat in the car is compatible with her booster and not much else). In a booster, the seatbelt is easily tangled. It's kind of a pain so you have to watch each time, to make sure all is good.