For me also somewhere around 9, and that was in R+A events, where most of them were dubble rebuys. Its not something, I really recommend, because it can magnify a losing session, and often tilt will be at least somewhat present, if you get felted again and again in the same tournament. So often better to call it quits after a few attempts and wait for the next one to begin, even though in theory each invididual rebuy might be a +EV decision in itself.