For perspective, an AGM deep cycle battery capable of higher resting voltages and greater reserve than your typical battery won't need you to rely on an external charging source each day- depending on the charge deficit it sees in your application when charged solely by the vehicle, it will require a top-up on an external charger periodically (maybe once per month depending on usage). It is easy to see with a multimeter exactly when that will do some good. The main reason for that top off to full charge is to avoid running in a partial state of charge for extended periods. Use at PSOT impacts AGM batteries as well as standard flooded lead acid batteries.
You can install an AGM deep cycle and use it just like you would with any other battery, but the down side is that partial state of charge will prevent it from lasting as long as it potentially could. Would it still outlive a flooded lead acid battery? Quite likely, but it might not last 5,6,7,10 years as it would when topped off. If you are paying big bucks for a really strong AGM deep cycle battery, it seems a shame to allow it to fail earlier than it otherwise would.
