beside heat, all old classic lcd's don't like pressure at all, they are fragile on mechanical effects ! Put your fingers too strongly on the screen can cause a bleeding effect, as they were toys for children, I can imagine this can be one of the reasons for bleeding in general?
my experience is, if you stock your games in a dry, standard temperature and not direct sunlight environment, you won't have troubles with bleeding, or let's say at least in all those years I am collecting, no single Game had suddenly a bleeding issues...
cheers, gameandwatch
