If the girl is clean it won't matter what time you go.
If she's not it still won't. The dirty ones will wipe you off after the punt for her comfort, not clean herself for yours.
First punt of the day gets you whatever has ammassed there since last punt yesterday. Overnight deposits by partners, friends, toys, the family pet, or whatever, plus sleepy-time-funk, smeg and of course the ever popular dried piss deposits.
All good fun really.