Are these shortened sessions in rented or private dungeons? When renting from someone there is pressure to get out and have the room ready for the next rental as soon as possible. Cleaning time for some is included in the client's hour.
I know many dominas who start the clock when the client enters and the domina is still in street clothing. You want a session with a latex domina? Well 20 minutes of your hour will be her wiggling into a catsuit.
Everyone is free to do that, but this is a business of limited clients and one cannot survive without regulars.
I often include the preamble, 3 minutes or so, and aftercare in the client's time, sometimes with a run over, but it's my place and I do as I want.
I just raised my rates but everything has gone up including my tax rate (45% now

), but I don't think skimming 15 minutes here or there will somehow save more money.