Yeah here's my deal with that.... No dive op tries to tell me how long my dive will be. I come up when I hit 500psi. and if its 50 min or 65 minutes then that's my dive time... If they don't like it I will take my business elsewhere. I pay for dives by the tank not by the minute... That is SO aggravating.
I would also be annoyed by an inflexible dive op that demanded a rigid time schedule and tended to cut the dives short but we do try to be considerate of others. If we are likely to take an extended period of time then we try to get off the boat early and quickly, so that others are not stuck sitting on the boat a long time waiting for us to return. It is just common courtesy because we all paid for a good dive experience.