Is it bad to spin motors to full throttle without props? I'm being told this in another post of mine, and I think that's wrong. You can run full throttle for a few seconds with no prop with no danger to the motor.

it is fine for a short time. This is not an internal combustion engine that requires a load on it. So long as your ESC can handle the rpm and the bearings are not over speeding (which is fine for the rpm we normally deal with) you are golden. They are you limitations.

here is an example of a motor running at more than double the usual prop speed with no load on it. Modern esc's can handle very high rpm without de-syncing. Oh and look at the date. This was when a lot of esc's were still struggling to keep sync on 4s with a prop on.