to answer the other part of your question..... my daughter is 11 1/2 and would STILL change clothes into a completely new outfit every 15 minutes if I hadn't really managed this behavior intensely from the beginning.
In addition, within the 15 minutes where she has decided on one outfit, she would be accessorizing with shoes, jewelry, arm warmers, headbands etc. before she changed again.
So.... I'd like to know when that naturally ends as well!!!!!!
However, NO I do NOT pick up her messes. EVER. She made the mess, she cleans it up. We figure that into the amount of free time she has. It's called teaching self-accountability and if you just allow your daughter to go through life like a tornado expecting others to clean up behind her you aren't doing her a favor.
The boundaries I set for her were the following:
1. If she's in her room having "free time" it has to be when all her other "stuff" is done - ie homework (coming for you in a couple years), practice piano, her stuff picked up from around the house.
2. About 20 minutes before her free time ends, I go in and survey. Then I tell her she has x amt of time left before she needs to start cleaning up.
3. If we have to leave somewhere at a specified time, that is the time we leave.... regardless of whether she is "happy" with what she has on or not - or if she decides at the last minute that she wants to wear something else. This took some coaching (and you have to give warnings about how much time before we leave etc). I kept some really funky clothes in my car so that she would be weather appropriate (ie - a big oversized sweatshirt coat and funky shoes with unmatched laces). Since she found out the hard way that I was serious and that she really was going to have to leave the house, she did a better job making decisions and getting ready in a timely manner.
4. Even when she was little, SHE cleaned up DAILY - or before she changed activities (but I helped her - which means I actually DID it, but she had to be right there and I gave her simple commands - pick up that dress and put it on the hanger, now hang it on the bar. nope, so the buttons are on the left. yep that's right, now pick up the blue shirt and put that on a hanger.....)
5. I only wash clothes that are actually DIRTY and/or that have been worn for at least 1/2 a day. If she tried it on and 30 min later decided not to wear it, she hangs it back up. now that she is older, she pretty much does her own laundry - but we still sort it together so that I can make sure she isn't just re-washing stuff that fell off the hanger.
6. My clothes are not play clothes. I wear them to work and they cost significantly more money than I am willing to just replace on a whim if she trips or whatever and they rip. I have "GIVEN" her some of my old clothes when I was going to get rid of them, but NEVER would she be able to put on my work clothes.
7. She is allowed to wear my old t-shirts around the house, but just like I don't go get in her drawers in her room, she doesn't go get in my drawers in my room. We are a very open family, but I believe wholeheartedly in personal space and boundaries. So, my room is not off-limits, per say but she can't just go spend time in there.
If you have a great play space that is your closet, I would maybe consider doing something else with your clothes and turning this great area into her play space. you can get wardrobes pretty cheap that look nice in the room and have hanging bars. That way she doesn't have access to your things, but can still feel like she can go in that great space.
Also at 4 my daughter was still fairly heavily supervised. There wasn't time for her to make that much of a mess, even in the 10 minutes I might leave her in a room unsupervised. I did most of "my" activities after she was in bed, and so the entire time she was up and active I was involved and either playing with her, she was helping me, or we were doing an activity together.
Now that she's older she has learned how to make better decisions and how to have more impulse control, so she can be in her room unsupervised for longer amounts of time.
Just my $0.02