I've read the prior posts on the 12 volt life expectancy but nothing posted on the Optima life expectancy. I'm used to purchasing a 60 month battery and then just replacing it in about 36 months. That seems to provide a measure of safety,of not getting stranded with a inop battery. I'm assuming that the OEM 12 volt should be reliable for about 36 months and the Optima should last longer, but the Optima web site claims free replacement for 36 months nothing further ???? Anybody have actual and factual comments to share ???