I don't know where the eight-hour rule came from, but it seems arbitrary. I've been binding about 16-18 hours a day for the last four years, and I'm just fine. If you can get away with binding fewer hours, that's probably ideal, but I wouldn't worry too much about wearing it a little longer than recommended. And obviously, if it starts to be really painful or you start to have trouble breathing or anything, you should take it off. But that's only ever happened to me three times over the last four years, and all of those time I had been wearing it for WAY longer than I should have, so you probably don't need to worry about it.