I think.both of you have valid points.
Heat is a killer but I think a frequent heavy draw on a lead acid starter battery also shortens battery life. Such as that from glow plugs and starter demands of a cold engine.
Proper battery and charging system maintenance by making sure all cable connections are bright & tight, cleaning posts, using felt washers, occasionally topping off with a goid charger, etc can all help to protect the batteries.
I have also read the common practice of trickle chargers is also a battery killer.
And, again, you guys are both right, 2-5 years is the typical life of a lead acid battery.
That's why I switched to Odyssey extreme 65-PC1750T batteries, because I was only getting two years per set of batteries. Hopefully, I will get at least six years with these.
2001 F350 XLT 4X4 crew cab, dual rear wheels, long bed, black, 7.3l turbo diesel, automatic transmission, 4.10, shift on the fly, running boards, sliding rear window, 38 gal fuel tank, Odyssey extreme 65-PC1750T batteries, Michelin LTX-MS2 rear tires, Sumitomo Encounter front tires, Shell Rotella Ultra elc, 11,500 gvwr, 20,000 gcwr, 7500 gvw, completely stock, 114,000 miles when purchased, now has 240,000 miles, repairs so far: two starters, batteries, cps, brakes, tires, alternator, ball joints, locking hub, wheel hub, AC compressor, serpentine belt, power steering pump, driver's side window, ignition switch, o-ring, Spectra premium radiator, water pump, fan clutch, fan blades, thermostat, thermostat housing, tensioner. Stolen twice so far, but recovered both times with major damage.
2005 Nomad Rampage toyhauler made by Skyline. 11,500lb gvwr.