As an aside, I have two OEM Deka DC-24 batteries that I put in the camper the day we took possession in June 2009.
We are plugged into the converter 24/7 while in storage
We spent two winters boondocking in Key West (Sigsbee Key) (a total of more than 180 days) and lots of off grid camping since (though not so much any more - sigh).
Been waiting for these to die so I could upgrade them, but they refuse. Properly cared for you can get many years out of a pair of even cheap batteries.
Most likely we will upgrade the camper before the batteries now
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW