I still have my old clothes 10 years ago, and they still look good and I can't let it go yet even it doesn't fit to me anymore. I am trying to loose some pounds so I can wear them back. I always keep my clothes fold and make sure it doesn't get where I store it cause it becomes moldy. I hate winter because of this reason, cold sweats can make your storage molds if you don't check it every now and then.
Proper washing, dry it our completely and it's also depends on what type of clothing you have. There are some types of material that doesn't last long. Since we don't have proper storage at home, I store my old clothes at the traveling case. Some of them I am still using especially the one is stretchy. Mostly, that doesn't fit me are my pants and some dresses. Some old clothes I have been given to charity so someone who has not enough can wear it.