An automatic shut-off feature is the best way to go for convenience and efficiency. You won't have to worry about remembering when your vibrator runs out of power, or even worse, accidentally leaving it on and draining all your batteries. It's also easier than having to carefully monitor how long you've been using it so that you don't run out of energy or batteries before finishing up—and this can be especially important if you're using a couples rose sucking sex toy with its highest setting! It can be tiring enough trying not to fall asleep while enjoying yourself.