I have a 20 yr old in college and a 22 year old who is working.
The 22 year old was living in an apartment nearby, but moved back in last year with a new dog that needed a yard (whole rescue saga there I won’t go into). We did a big decluttering of our basement and the kid repainted it and fixed up one of the rooms down there as a bedroom and we are repurposing the upstairs bedroom into a cat room/office for DH (and the cats).
Our 20 year old got herself a girlfriend in college and spent last summer fixing up her room (repainting, new bed) so it didn’t look like high school when her girlfriend came to visit. So it’s still her room, but very different from what it was when she was in high school.
I grew up as the youngest of 3 kids in a 3 bedroom house. When I was little my older sister and I shared a room. When our older brother (9 years older than me) went to college I took over his room. But when we were all grown and would come back to visit for the holidays, etc, my sister still claimed “her” room, and my brother claimed “his” room and I got to sleep on the fold out couch. This still happened when my husband and I had kids and my brother and his wife didn’t have any. I guess we could’ve gotten a hotel, but it was fine, really. Just funny that no one ever volunteered to give up “their” room for us.