My boyfriend binds for long periods, sometimes 2 days solid, and it has me worried. He'll sleep in it, and sometimes I'll roll his arse outta bed and make him take it off. I really feel for him, though, as he hates his chest and it causes him a great deal of mental anguish. It's only natural to want to turn that mental pain into something else, because the physical pain can be managed much easier than the stabbing mental mockery even a single errant jiggle can cause.
On another note, I've heard that binding can actually cause a temporary reduction in the apparent amount of tissue as it compresses and "breaks it up." It sounds possible, maybe through fluid reduction, though likely any tiny result is not worth the health risk. Anyone else heard that?