The coach batteries in my motorhome are starting to show their age (6 years old) (accelerated because I once accidentally drained them to dead-zero) and I need a couple replacements. The current ones ...
Not sure how you have six-year-old batteries in the 2013 motorhome? For your usage I would go back with a single AGM battery and forget about it for six or eight years. Yes, I know you said no AGMs but once you've had them you'll never go back to the regular lead acid batteries.