I plow snow commercially, 2 years on any battery is about all I get before problems start arising. had all different kinds including gel types. the High current draw and the pounding/vibration tears them up internally. Even had a yellow top optima( close to $300) -lasted just past warranty - shorted internally. Internal breakdown is what I mostly run into not an age factor. another factor is the alternator output really doesn't start charge wise until about 1500 rpms ( eng) on most vehicles. alternators that start outputting at say 900 rpm(eng) are pricey, hard to find also. It gets a little dicey changing out the pulley diameter on the alternators as well with the serpentine belts.
Part of the deal on batteries today is they make two kinds, a winter battery then a summer battery. Or the manufacturers call it a northern batt and a southern. Apparently, they can make one more heat resistant, but it won't crank good when it is cold. If it cranks well cold, then it starts to deconstruct itself once it gets hot.
The optimas allegedly were pretty good until a couple years ago when they moved production to mexico and changed the lead content, etc. Made em lots cheaper but charged the same money for them.
But ya..nothing I have tried lasts long anymore. Used to be in ye olden daze I could get around 7 years from a battery, now like you said, two years.
I know you can get a *real* expensive lithium ion truck battery now, hopefully this tech will keep getting cheaper.