I feel that major edits and redos should only be possible in the sketching and maybe inking process, and instead of 10 minor edits per art process phase, maybe 10 in total if you're worried about being stingy. But I feel 5 edits in total should be more than enough, with the option of a redo in sketch phase. There's also this thread here http://artists-beware.livejournal.com/764726.html in which other artists explain their methods for changes and edits!