I have replaced my battery 1 time since the car was built. I didn't wait until it quit charging. I remember Mike laying on his back during Route 66 replacing his. Too much to worry about so I just replaced it after 4-5 years.
I got two small Optima gel otor cycle batteries that are mounted down in the noise side by side long ways. less space. This way when you go head on into someone or thing the batteries will finish you off?/@!