My brother and I have a simple rule: Once a firearm comes into our position, it does not leave! We don't even trade between the two of us. Several years ago he got a honey of a deal on TC Encore ($150) but he doesn't do much black powder hunting. So, he lent me the rifle, I put a scope on it and change out the primer removal lever….Now I've got about $150 into HIS gun! Every year, at the end of the season, I clean it up and give it back. Then, next year, I pick it up, check the zero, and hunt with it all season.
I think we get it from our dad. Sometime in the 70's he stopped trading firearms because he would always end up with traders remorse.