We normally do 2 - 3 trips a year to campgrounds that do not have hook-ups. For us it was worth it to go to a pair of 6V batteries. We also changed all our interior lights to LED's and on our last 3 day trip the batteries were still reading 2/3 on the panel.
I don't feel the need for the AGM batteries though. Check the levels maybe 3 times a year and you are good to go. Do not let the water level get below the top of the plates in the batteries. Refill with distilled water. If you need to fill more often than this then chances are your charger is cooking the batteries