I ususally stick to buying just M/NM level comics. I never buy anything below that. However when at cons, if there is something I need to complete a story I'm reading and it's in 25ยข bins, I'll make the exception and hold out till I can gind a reasonably priced better condition copy for the collection.
When it comes to older stuff, I usually just skip back issues and go straight to the trades if they are available.