I think that DD is old enough to learn how to put away clothes she's discarded. No, she won't probably fold them neatly for awhile, and you may need to double check frequently that she hasn't put DIRTY clothes away too--but my DD is the same way (she is 8 now), and I taught her to put stuff away at 2. That was the condition of allowing more than one outfit change when she was little. Now that she has after school activities and often plays outside when she gets home and wants to have a school outfit, an at-home outfit, and a going-out-later outfit and she tends to get all three dirty with food/dirt/sweat/ect...we've had to change the rules a bit. She's limited to two outfits per day. We did make a deal that now she is tall enough to reach alll the knobs on the washing machine I would show her and supervise her doing her own laundry this summer until she and I were confident that she was skilled--as long as she does her own laundry, which will include getting stuff in the dryer in a timely manner and putting away clean clothes--I really don't care how many outfit changes she has. She's really excited about this right now, but she is a bit on the lazy side, so I suspect after a month or two she will limit her clothing changes and/or monitor how messy she gets so she doesn't have to do as much laundry.
Oh, I forgot to mention--I found weeding clothes and not having drawers bursting with clothes helped immensely too. Both in how many outfits she could go through in a day, but also to aid her in being able to stuff her clothes back in the drawer. Now that she is older, I still keep an eye on how many clothes she has, but she is very into accessorizing now and that has been very helpful. One of our projects this summer is to build, paint, and mount some kind of storage for her many scarves, shawls and shrugs and hair dodads. I think honestly that accessories have helped a great deal in cutting down outfit changes. But since she had the unfortunate happenstance of being First Kid I did not allow her to have scarves as a toddler because I was afraid she would hang herself accidentally or tie up the babies.
Maybe if I had allowed her those earlier I could have saved $$ in laundry detergent. ;>