If the fly is used... It usually goes into a catch all sort of box. You don't actually want to see it. It sort of looks like something the cat threw up...only a lot bigger. I actually get quite a collection over the season...but I also visit that box first when going out and yes I reuse my flies. If they caught fish before, they will catch fish again. They get tossed when I can't get a sharp point on them any more or the fly doesn't preform in the manner intended...ie floats when I want it to. I don't mind beaking them off if they get snagged up so it lets me fish them harder and get into more difficult situations, because I no longer think of them as my cute little buddy. Not that I did before. Thus they often end their lives honorably, on the battlefield.
I just spent the last hour reviving my whole Hex and Drake collection (all used) I dug them out today and it looked like they were stored under a stack of books all year. It's amazing what getting them wet, then hitting them with a hair dryer will do. I wish I took a before and after photo. I just saved myself about $75!
remember...the first flies were nothing more than a small hunk of wool thread stuck on a hook.