Wow, this seems to be everyone's question...
No, it has never happened that I wanted to be the Dominant when he wanted to, as well. We have taken turns on the same night, though. Granted, it's a bit hard to make that mental switch - but if the cooling down, aftercare is long and satisfying enough, then it isn't that big of a challenge.
"I assure you, Your Honor, I don't have to practice...I'm very good at them..."
(The Marquis de Sade at one of his trials for the sexual perversities he practiced)