Every guy knows when you hit the cum launch sequence...Every time you jerk off you know exactly when. About 2 seconds prior to initial blast you get that feeling that the engine has lit and nothing will forestall leaving the earth lol. So cut the crap. That warning is enough time for her to bail out if that is her desire. Making women do shit they don't want to do is the fastest way to rocket to the top of the complete asshole power rankings.