When we got our rig in 2010, at 8 years old from the original owners, it had one very tired battery in the house circuit that wouldn't hold a charge for more than about 6 hours with nothing switched on.
The battery tray had room for two batteries, so I headed to Costco and got two of their deep-cysle RV/Marine 12-volt batts. IIRC they were maybe $64.99 each. Still going strong, coming up on our third season. NADA was my source for the battery inter-connect wiring to get the two of them wired in parallel.
We don't boondock, so the high capacity golf-cart batteries aren't necessary for us.
Frank and Eileen
No longer RVers or FR owners