it takes a long time, because its a risky decision. I am not talking about the financial cost-which can be significant for many- nothing is worse than hearing no chemistry encounter, its basically paying to get humiliated and hurt.
This used to be much less of a concern in the past because most SPs back then would have provided a basic minimum service regardless of chemistry-one can say they had better work ethics- but those days are long gone .
now its almost like a normal date - you pay intimacy might happen or not- with one big difference, dates can still be enjoyable even if the intimacy does not happen, one can enjoy the food, the show (or whatever the date activity was), but in case of meeting a SP all comes to intimacy, and if that does not happen its a horrible experience