I've never endo'd. I hit the front brake hard enough to raise the rear wheel several times a year, but I haven't endo'd because, like most people here I'm sure, I've taken the time to learn to use the front brake properly.

Also, if you're braking hard you should automatically shift your weight back as far as possible; in fact for most people you can wind up sitting on air behind the saddle.

I've never hit something hard enough to flip me (I'm pretty conservative and don't curb hop and stuff like that).