Quote//When you are plugged into shore power or on Solar, what is your maximum battery voltage? 13.7 VDC is the maximum you should see//Quote
13.7 volts ? is this float, absorption, bulk voltage? I wasn't sure what you meant.
If you have the stock GoPower! charge controller installed by LTV, even though the product manual says that it is temperature compensated, there is no sensor attached to the unit that goes to the battery box. If it has a temp compensated function, it must take its temp from the coach, not the battery post. Not optimal.
Though lead acid battery AH capacity diminishes some with age and can take a hit from repeated full discharges or not watching water levels, the biggest issue over time leading to diminished battery life may be chronic undercharging. This gets back to having proper charging algorithm with appropriate voltages for the battery type. I know that all charge controllers have lead acid, AGM, etc settings, but a call into tech support for that battery manufacturer would be a good idea to get their recommended charging parameters.
I learned a lot about batteries, charging, etc, from reading this long web page.
https://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/
Also, in response to overzealous recommendations from some battery companies in the last couple years:
https://handybobsolar.wordpress.com/2018-warning-turn-the-voltage-down/