Good discussion. Thanks all.
Jay hit the nail on the head: Go back and re-read Nigel Caulder's book. That's always good advice. By the way, I have three charging systems to tune, shore, alternator, solar.
The first thing Nigel says is to assess your needs and use requirements. Because we boat owners have such different patterns of use, anecdotes about what did and did not work for me, are not always applicable to others.
I live on the boat 365 days per year. 10% of those days on shore power, 15% on engine power while under way, and 75% solar power while at anchor. Out total consumption is 30-40 amp-hours/day. 75% of that consumption is to run the 12v refrigeration system.
Then I think of Jeff&Wendy on the W32 Calypso. They have an icebox, and no solar. Their use patterns are very different than mine. Then I think of Jay on W32 Pygmalion. Jay sails on weekends only. His use patterns are different still.
The point is that one size fits all doesn't work.
Tate: Thanks for the info. I had my starter battery as bank 1 and the two house batteries as bank 2. That was perhaps not the smartest way to do it.
By the way, Tate, I looked up that Xantrex splitter device. It costs $125, as much as a new battery, and I don't see what it accomplishes more than a $3 diode.
But Tom might have had the best advice about saving money on batteries. An engine compartment blower. I was going to do that once, but never got around to it. It never occurred to me to relate that to battery life of flooded cells. I didn't know about the 50C limit for flooded cell batteries.
Once again, everybody's boat is different. Mine has generous lazarrete compartments port and starboard under cockpit seats. I love the extra storage space, but those compartments reduce the volume of the engine compartment by 40-50%. I'm sure that makes my compartment run hotter than most.