I think the domme will pee whenever she wishes to do so and maybe at the end and maybe not. Also, lots of dommes find it fun and dozens of dommes include without being asked, especially if it provides them a feeling of dominance, victory or they are happy to humiliate the slave. I mean there must be dozens of reviews in which the guy says she peed or sprayed him, on the first or second visit, after corporal punishment.

Maybe the thing is to ask which domme give a guy a shower without being asked and do so for fun. If a gal never does that, she might be a bit boring!