lowviz, some of us love cold water diving, but don't like diving cold! Through six years of experimentation, I've learned I can be quite comfortable in any PNW water for 45 minutes, and often comfortable for 60 if it's a single dive. It takes management, though. Multiple dive days take even more. I think it's uncommon for anyone to do three dives in a day in our waters and not come up from the last one cold, unless they are either so inefficient that they are moving constantly, or they are doing pretty short dives.
It's worth the effort, though. The OP seems to indicate that he or she is willing to make that effort.