Jon - My CC and the previous Marathon is like yours, it can set a long time with no problem and still have 24 + volts and I never turn off any of the switches. I suspect some of these with short chassis battery life when the switches are off is caused by a bad battery(s). One weak cell can drag down the group in short order. Even new batteries as we know can be bad.

Bruce - Letting the charge get to float assures you have put a full charge back in the batteries and the next cycle of use will last as long as possible. If you cut it off during absorbtion, your not getting a full charge. I experimented a little with this and it makes a difference. Also, remember 12.2 volts is 50% discharged.