Hey Pete
In order to make lectric the battery has acid in it that eats at the lead plates inside.. As these plates get eaten up they get thiner and thiner.. When offroading a bump in the trail can cause one or more of the THIN plates to come loose and cause a SHORT in that cell.. that results in a battery with only 10 volts (if you are lucky).
So with that in mind I try to keep a battery that still has THICK plates in it when offroading.
Also if the battery is kept in clean condition and is not discharged much...as in parking and listening to the radio all day.. it will prolly last longer.
I have several different colors of paint pens, which I use to mark EVERY battery with the date of purchase.
I look at it thisaway... Say a battery with a 36 month free replacement costs $60. After it is 3 years old it has cost me $20. a year. Hell! That is a bargain for KNOWING the thing will start the vehicle no matter where it is parked.
So I exchange it for a NEW one, and start all over again.
In my younger years batteries were not as reliable as they are now. I had many dissapointments with them. So maybe I am too careful now.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />