Replacing house batts? 2008 RT Popular

[Kegan]

Are my house batteries dead, dying and just need to be replaced?

I have 2008 RoadTrek. Went out for my monthly "run the generator a couple of hours" maintenance routine. Could not get the generator to turn over, though it was trying (clicking). Started the vehicle, let it run a bit, presumably charging the house batts and generator started right up. Couple of weeks later, same scenario and same outcome. My gut tells me they are in need of a change. Unfortunately I don't know how old they are and the stamped in date code is not readily accessible. I do know they are at 3.5 years old, as that is when I bought the vehicle from a dealer.

My questions:

1. Any harm in continuing with the weak batteries for the short term at least, provided I understand I need to be on Shore Power or Engine if batteries being used

2. When I do change the batteries any recommendations as to changing technologies (Li, etc) I really do not want to have to mess around with new inverters, charging devices, etc. however.

3. Prior to changing them out, is there any way to blow a little more life into these. I presume they are sealed, though it does seem there are ways to add water or check electrolyte.

Current set up is Interstate GC2-HD-AGM (see picture)