Much folklore and little fact
AGM or wet, in typical RV use while camping you can run them down to 80-90% DoD provided that they are recharged promptly. Yes it will reduce the cycle life but in typical RV use that isn't why batteries die. Your Airstream is not a forklift or a floor machine and the batteries are not discharged and recharged 365 times a year.
I run mine down to 80% DoD when I need to which ends up being maybe 3 or 4 times a year at the most. Flooded group 27s. Still going strong after five years.
It is the situation where the batteries discharge in storage and then remain in a discharged state for a long period of time or in freezing conditions that leads to damage.
To learn to see below the surface, you must adjust your altitude