"I would say something’s not quite right here. My '01 Jetta is on the original battery, and so is my '04 4Runner.
“There must be something happening that they die so completely when they do. Every single battery I’ve ever seen in a car dies a slow death, and even at the very end, there will still be enough power to turn on things like lights, etc, even if there’s not enough power to start it.”
I wish I knew what was happening. Previous cars I’ve owned have also had their batteries die a slow predictable death like you describe.
I drive this car almost every day. Five days a week I make a 30 mile round trip commute to work. I live in central Texas so we do get triple digit heat for for about 1/3 of the year.
I bought the car used in 2/2002.
The first battery, which I assume was the original battery, died in 11/2004. I was out running errands all day. Everything was working fine. I stopped to get gas. When I went to restart the car, nothing. The electrical system appeared to be stone cold dead.
I was so shocked by how completely dead my electrical system was, I took the car to the chevy dealer to have it checked out. They checked it out and said it was fine and I just needed a new battery and cables, which they installed for an outrageous labor charge. I decided to never go back to the dealer.
That second battery died about 2 years later in 8/2006. This time I took the car to National Tire and Battery and purchased the cars third battery. They said the car was fine and just needed a new battery.
That battery died 2 years later in 9/2008. For reasons I won’t bore you with, I was not happy with National Tire and Battery either, so I cut the cord with them (even though they might have given me some credit towards a replacement) and this time I took the car to an independent mechanic I had heard good things about from friends.
He said the car was fine and just needed a new battery. He installed the cars fourth battery, which is what I have in their now. It will be 3 years old this coming Sept.
So the short battery life problem is actually worse than my original post described. I’ve been replacing the battery every 2 years. (I was relying on my faulty memory in my op, but this afternoon I checked my written records.)