We lived in a 1400 square foot home when I was growing up. Now that I look back, I don't think my father ever got rid of anything. I went to help him clean out the house before he moved, and we filled up a 15 foot long dumpster to the top and still had enough stuff to fill a 2000 square foot home. It was like an adventure going through each closet that was filled to the brim with stuff. At the time, I wasn't as careful about what I threw away because I only had a few days. Now that I look back, I probably threw away things that were worth some money. When I was first married, I also helped an older lady in our church go through stuff before she moved. They were wealthy and had tons of stuff. They had a storage unit for 15 years with stuff in it that they never looked at. I went through some of the stuff, but they ran out of time and her kids just had Goodwill haul it all away. 15 years at 100 dollars a month and they just hauled it all away to charity.
Go through your own stuff and keep it under control so you don't leave a mess for your kids. On the flip side, kids shouldn't expect their parents to hang on to their stuff and clutter their parent's house. When you get married or graduate form college, take your stuff with you. A friend of ours had a daughter who didn't want her stuff she had growing up in her new home because it would make it cluttered. It is your stuff, so take it and do what you want with it. If you don't want it, then give your parents the freedom to dispose of it. Don't expect them to hang on to it.