RE: Which ESCs keep brake on indefinitely ?
If you're not using a folding prop then it's going to windmill to some extent even if the brake is on all the time. An "always on" brake is simply one which shorts out one or more of the "phase windings" on a brushless motor. And at the sort of low RPM you get it can still windmill at anything other than slow to moderate flying speeds. It just won't windmill as fast as it would otherwise.