If I have to shower alone, does the time involved come off the session? What per centage of the women will join in a shower?

....on the provider/house.  One place I go to in NYC doesn't start the clock until you're out of the shower and the provider joins you in the room.  Percentages?  I don't know.

Reoes shower time count?

Without trying to sound too negative, yes, with most escorts every single second counts. I have had a few "no time limit" sessions, but believe me this is the exception rather than the rule. Most girls will say $300 per hour and collect exactly that amount from you when they arrive. Then call someone to let them know they arrived and all is well. After a few minutes of small talk you usually get down to the action. Most girls will start trying to get you off as soon as they can. The sooner they get you off, the sooner she can leave. Don't fool yourself into thinking she likes you. This can happen but like I said, it's the exception and not the rule. Over the years I've been in the hobby I find that once the girl arrives her meter has already been started. That's why it's up to you to make the most of the time. I know guys who try to seduce her, but face it that's already been taken care of. They just end up wasting time. For the most part, about 35-45 minutes is all you can expect her to be working for you in an hour long session even less if they can get away with it. Then you're just a past customer to her unless you've got another $300.