It's become way too technical for the OP now that BFL has saddled his favorite tilted horse :)
What Don and SMK said:
Between the trips it will keep batteries topped up while in offgrid storage, thus extending their life. Not worth spending a grand or two, given the cost of 6V batts. Hardly worth spending, if your rig is on 120V maintenance grid while in storage either.
On an offgrid trips in AZ in winter it might let you camp without ever running a generator, though with a lot of conservation efforts, which includes optimizing and replacing some of your trailer devices. Some people can live on 40 AH a day. Some need 140.
On camps with hookups - can't say. I avoid camps with hookups unless camp is not too crowded and price is not too high, which doesn't usually happen.