Beeryboats
I am using the odyssey PC-680. I do have a dual electrical system with a cross tie so one 680 is on the firewall and the other is behind the Pilot's seat. ....8 years running and the voltage under load (cranking) and after sitting is still right where it started when both were new. The voltage under cranking load tells a person somewhat how a batteries capacity is holding up. Odyssey has a specification for what the voltage should be when it is sitting and not connected to a system.
This weekend the weather gremlins were asleep and I fired up the kitfox after sitting in the hangar for 2 months (the plane...not me; and, yes I am ashamed the plane sat that long!) and it started right up like it was last run yesterday....and that is without a battery minder during the hiatus.
Don't ever waste your money on a knock off AGM battery from batteries minus......they are crap in my limited experience.
I think your experience with the wet cell is about what a person can expect from them.