some agencies (brothels) i have worked for in the past usually back to back clients if they can as they dont want to miss out on money if the client dosnt want to see another girl. generally if a girl is booked from 1-2 she should do the booking until 2. generally the other guy will come at 2 (or usually 10-20 minutes after as some punters dont arrive on time) however if the guy is bang on time then the receptionist/maid will show him in and make small chat offer him a shower, drink etc and waste 10 minutes so the girl can quickly shower, get ready etc and then the girl will go into the client while the receptionist/maid cleans the other room ... thats why maids get tipped so much. generally nowadays a agency girl wont be back to back so much that this happens every single day. theirs generally a rule that if a girl has done a certain amount of back to back bookings then she has to have a 20 minute break after a certain amount. think its usually 2 hours worth of bookings
btw, not saying this is how all agencies and girls work, just what I have experienced in the past from agencies, parlours etc