For me, there is something about it being dark when I go to and leave a session that makes it feel right.

I also do like to have time to prep my body (eat right, clean myself out, etc...) before a session and that is very difficult for morning sessions.

However, I generally let the Domme decide when we meet and I want her to feel at her best more than it being the best time for me (since her feeling her best means the BEST time for me :)).