and much depends on your training and WHERE you learned to dive.
My cert dives were done right at the 60' maximum - the final two were done at 57' to the sand. Why? Because there is really nowhere to dive around here that is more shallow than that, other than the jetties.
Seriously.
Even the "weenie" dives around here - those less than a couple of miles from shore - are in the 70-80' profile range. I was doing them almost immediately after getitng my OW.
Why? Because I was trained under those conditions, and was comfortable.
Now it DID take me a while to get to the 110' that I dive in now a good part of the time. But "a while" wasn't 500 dives - it was more like 50ish. My AOW "deep" was a joke - I had already been deeper, on many occasions, than the "certification" dive for that purpose called for. I was already familiar with the issues involved, with the higher gas consumption, and the added risks.
A think a lot also has to do with how often you dive. If you dive a few times a year, but do it all in concentrations, that's not nearly as good as if you dive a good part of the year, at least a couple of times a week. I do the latter. The only reason I'm not wet right now is that the water is pretty cool, my buddy's tolerances have been exceeded, the weather has blown tomatoes and my boat is down right now for spring maintenance. Those issues will be resolved here within the next couple of weeks, and then it will be back in the water for me. I had about a month lay-off here, and my speargun trigger finger is getting itchy
If you learned to dive in the carribbean in 20' of water, then no, you're not going to be ready for 90' in 10 dives. But if you learned in 60' of relatively murky water, and everything beyond the one place you were certified was 70-80' or so, in 10-20 dives you might well be ready to be approaching the triple digits, depending on how much of an effort you made personally towards skill acquisition and familiarity with your gear.
I have a general rule that I only make one change at a time in my configuration. So, for example, this summer I will dive double HP100s. In OW. I'll do two dives with one set of tanks, sequentially, without changing over. Why? Because then its one change to incorporate deco procedures, or perhaps cavern, or whatever I do next. Second, I gain redundancy on my 110' spearfishing dives, in that I have two manifolded sources of gas, two firsts, and two seconds. All the better to stay alive with.
The compressor, by the way, is not that big a deal. Depends on why you want it. If you have your own boat it makes perfect sense, as going to the shop to get filled between two diving days SUCKS. Been there, done that, and I hate it. You're subject to their hours and whims, and if they are busy, you're hosed. How many tanks do you want to have laying around the house? Why more than you need for one day of diving? No good reason if you have your own fill station - and can afford it. There is also a significant cost savings on an amortized basis.
BTW my drysuit was a non-issue within a couple of dives - but I don't use it as a BC. I dive with the dump all the way open and put air in to avoid squeeze - that's all. On ascent its "not there" as a task loading issue, since it just bubbles out - no manual intervention required. On decent its easy - get squeezed, give a (small) shot of air, ok, we're back to it. It has little if any effect on dynamic buoyancy dove this way - I still use my wing for my BC....
Anyway, some stuff to think about....
