For 30 minute bookings I think it's acceptable, otherwise it's quite a bit of work to get you hard and cum multiple times in 30 minutes. I don't think I'd find that enjoyable and it's a fair about of pressure on both parties. However, each to their own.
I'm a cum once in a booking person, so cuming once is fine but I don't expect to get nothing else for the remainder of the booking. I'd expected a snog or a lapdance or a BJ or RO or something not a dressed chat. You live and learn.