Demolishing a house

I never had the parents move out but things would be left behind wouldn't they like a dirty dish stuck somewhere? Or maybe something invisible stuck on the lot. I always let the parents die out and then move in the college student or they move back to inherit the land before the parent dies. That way I don't lose their family heirlooms and didn't have to redecorate the old house. But it runs the risk of a bugs on the lot, unseen. I have added on to existing houses after parents have died off etc. and I did keep their urns or headstones or move those to community graveyard. But all lots develop bugs after generations of Sims living in them. It may or may not cause ain problems for a very long time, but generation after generation of glitches can build up eventually. You may not see any problems for many generations. I wouldn't worry about it so much, until you start to see problems. Moving them in and out again can sometimes get rid of a lot of stuff. The Bat Box from Pescado can clear up any stuck/invisible visitors on a lot which is usually a problem after years of playing one lot.