I'd like to see as many instances reused without getting rid of the original like what happen to 40 naxx. The more instances = better. If you don't want to run them you don't have to. It's not like you'd be running stuff that you got sick of. Did you seriously run deadmines/RFC more than say 5 times on 1 char? I've ran the same heroic 5 times in a week before much less the lifetime of my char.