I am using Excide Mega Cycle GP 31 AGM for cranking and Optima GP31 for trolling. I bought one trolling battery in 2014 and the other was put in before then, Both are still working great. The cranking battery I replaced last year. The old one was put in the boat in 2008 when the boat was new. So needless to say I went back with the same battery.
I will say I got away from on board chargers in 2014. My onboard charger went out and that is why the one trolling battery went bad. I now use three Schumacher Ship N Shore and have not had a battery or charger since then. It takes about 1.5 Minutes to hook up but the peace of mind is worth it. IMO