Cindy,
I dive two to three times a week. I started out with doubled 72s (and if you ever want to come up and try them, give me a holler). I'll confess that, at the beginning, I dove Cove 2 and Edmonds exclusively, and only at high tide so I could minimize the walk! The problem was that I've never been able to trim the 72s out properly, so I've always been out of trim. When I had the opportunity to try a set of 85s, I did, and it was an immediate enormous relief. They're not that much heavier (they're not THAT much heavier than the 72s, to be honest) but they trim out MUCH better. And 170 cu ft of gas is enough for any dive I'm ever likely to do, and most of the time easily enough for two of the dives I usually do (sometimes three, if Edmonds or skills is involved).