Tried a 6 am session once, with a provider whom I knew well, and we had both told each other how we were "early morning people"...
Well, even though we were both "early morning people", getting up at 4:30 am and trekking over to her place for a 6:00 am appt took its' toll. She didn't seem quite 100% either.
So I continue to be a later-in-the-day perv...