I'm sort of "new" to SCUBA, but have 30+ dives, 27+ here in Belize, in the last year, so no "novice". Can you explain to me how a dive shop "offers at least an hour bottom time"?
Isn't "bottom time" determined by depth, diver activity effort & experience, breathing rate and numerous other variables? I've been on many dives, my earlier ones when I was just getting the hang of things, where I was at 500# at 30-35 minutes and had to wait 10-25 minutes for the last of the group to surface. I did the same dives last week, 9 months later and came up at 48 minutes, with 700# left in my tank. (I chose to ascend, as everyone else in the group had been up for 10 minutes or so.) My increased bottom time had nothing to do with the dive shop "offering me more minutes", it was the result of my increased ability, awareness & control.
While I dive primarily with one dive shop here on Caye Caulker, I believe most of the shops operate on a policy of ascending at 500#, rather than a time limit. If you can make 2300 - 2500# last 60 minutes, I'd imagine you'll do just that with most shops down here.