We go to some pretty remote, off grid, off cell service places. So, I don't try to maximize the life of the chassis battery on our PC or any vehicle for that matter. My experiences with OEM batteries have been mixed over the century I have been driving (well, just a little over half that long). Those of us of a certain age remember six volt vehicle batteries and generators, not alternators. The faster you drove at night, the brighter your lights!
In any event, I replace the vehicle battery every four years. Good battery, bad battery, questionable battery: 48 months and I go get a new one (usually at Walmart), put it in and I haven't had a battery failure in a long time unless I do something stupid and leave something on. Also, we need to remember about parasitic draining on vehicle batteries. Even when parked and stored they are discharging from clocks, etc. Every four years, out the door. That costs me less than two dollars a month to follow that procedure. Could I get another six months or three years out of a battery? Maybe, if I was lucky but it is just my little luxury of life for the price of a cup of coffee every month.
Paul