I'd like to comment on the dive times from someone who works as an ops manager, boat captain, and dive guide in the Caymans. Perhaps it's not always apparent to the customer - "what does 10 extra minutes make?" Often times it creates a domino effect on the rest of the day that isn't seen.
Just last week, we had a couple staying with us, who thought nothing of doing 70 minute dive times, after being briefed that 60 minutes was the maximum allowable time. This 20 minutes that we are now behind can easily turn into 30 or 40 when we get behind in the West Bay dock or fuel queues. This 30 or 40 minutes must come from somewhere - usually the employee forgoes their lunch break.
To be anywhere close to profitable, a dive shop cannot have employees just sitting around - they must be productive. To this end, perhaps there isn't an afternoon boat to go out, but employees time is sold to other customers to teach classes, to conduct guided dives, or perhaps a kids program. In the case of our couple last week, we now have a delayed boat, with 4-5 employees on the boat, or meeting the boat at the dock to re-tank it, who will all get no lunch break and be late for their next customers.
I strive to make my customers as happy as possible. I know where my paychecks come from. We like giving people longer dive times when we can, but many times this isn't possible. If you like to do long dives, then talk to us beforehand. I'll make my briefing short, I'll pick closer dive sites to the dock. Or take advantage of the shore diving. You can do 2 hour dives from shore if your SAC rate allows.
Also wouldn't be surprised if the poster's problem was that he asked if he could extend the profile. If you ask, they will almost always say no. But if you just do it, and they can see you under the boat at the end of the dive, I doubt they would say anything.
Most likely you are 100% correct. None of my co-workers would likely say anything, like we did last week. Most of us try to be kind, and know you are on vacation, and also live in fear of the negative trip advisor review, a gun which people pull out at even the slightest perceived offense.
We may live in paradise, and it may be a dream job. All I'm asking is consider when you are asked to keep the dive to a certain time, it's not because we are just trying to be difficult. Just some insight.