Some ladies do... and some advertise unlimited shots in a specified amount of time. I did a quick check to see if I could find such an ad in the listings here. I did not do an exhaustive search, but I did not find any. There are two other popular listing sites here in HK. I can't mention them, but you can Google them easily enough. I know that one of those sites does have such ads routinely (e.g., "45 minutes Unlimited Sex"). And others offer deals... e.g., "Full Set $250... Fuck Twice $350". Charming candor...
Have fun, CGP