Usually leave them on and regret it later when my hooks have spots of rust on them. 

I leave them on.  Other then very fine wire jig hooks, I have never noticed any rusting on any of my hooks or jigs.  I do let used lures/plastics dry overnight in a folded over towel in the back of my car before putting them back in the planos and also use zrust tabs in all my boxes. 

I glue 99% of my trailers on so... There is your answer. Its a habit that I picked up swimbait fishing for saltwater bass that has carried over to fresh water for jigs, spinner baits, etc.

I don't save them. New day, new trailer...And ALWAYS cut off a few yards of line and retie.