For either hybrid (crank/cycle) & true deep cycle AGM bank that is kept on float most of it’s time like in a holiday cabin or caravan that’s used maybe once a year for a week.
Then do these need to be exercised by cycling them a few times every so often?
I heard something about needing to mix up the inside, possible going bad if not used too much.
cheers
If a lead-acid battery sits for a long time, the acid can stratify a bit, and the resulting density differences can lead to eddy currents that sulfate the plates and ruin the battery.
AGM is basically a lead-acid battery but the acid is placed in a fiberglass mat (AGM = Absorbant Glass Mat). This makes stratification less of an issue, and the battery doesn’t sulfate its plates anywhere near as quickly (and even on a regular lead-acid battery this takes a fair amount of time to happen).
Exercising the battery once a year is probably sufficient.
Make sure your float charger actually monitors the battery charge level and isn’t just a stupid charger. AGM batteries are sensitive to overcharging and if you float it on a simple voltage-based charger you’ll ruin the battery in the long term.
And you can get smart chargers that test for sulfation when they begin to charge and apply rapid high voltage pulses to knock it off the plates. At least that is my take on what the owners manual states.
Dennis
Thanks 
From what I can gather this feature doesn’t work or is unreliable/unproven, only way to do it is with real equalization.