Yes - they need to be kept at least partially charged. They will go dead, possible in just a few weeks, if left to themselves. Also, they are subject to freezing if the state of charge drops very low, say under 60%. If the electrolyte freezes. The case cracks and/or the internal plates get warped, destroying the battery.
If you can't get some charge to them, either a constant trickle or a monthloy re-cahrge, remove the batteries and keep them in an above-freezing place. Even then, you need to give them at least an occasional re-charge to keep them healthy.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC