I've stored my 4Runner and not in extreme weather but it has a slow start how long does a heavy duty battery last without replacing it. Had the problem last winter drove a hundred miles or so stopped got back in, dead... just to find the cables were corroded. How often should I replace this battery for this vehicle it's had 2 batteries since I've owned it. Thank you
If the vehicle sits for a long time without being started, the battery itself will lose charge over time. Something like 5% of the stored energy will be lost per month, but this doesn't mean the battery will be dead or beyond recharging. It just means it may need a jump start when you go to start it for the first time after it's been in storage for a period of time. Batteries usually last for about five years as long as they aren't abused too badly.
Consider either placing a battery tender on the battery while it's being stored and/or disconnecting the battery from the vehicle as well. This will help the battery keep its charge for a longer time.