AGM batteries, overcharging on long drives

I have 4 deep cycle lead/acid batteries in my 2002 Chevy 190 RT and have had zero problems in the last 4+ years and I bet I will get another 3 or 4 years from them. Using a 3 stage charger with almost no loss of water, no boil over or gassing. I don't believe that this overcharging became an issue until the isolator was replaced by the battery separator and they started using AGMs. The loss of that 0.7 volt drop across the diode in the isolator resulted in an additional 0.7 volts being delivered to the house batteries when they use a separator and lead/acid can handle the additional volt better than AGMs.