Maybe you guys in the USA have it better than us in OZ, if you want to rely on your battery to start you every time, and not get stuck by yourself in the middle of nowhere, you change it out every 3 to 4 years max. I wouldn't take the risk any further if you want to rely on it to keep you going. That said I know some batteries will go 5 to 7 years or more, but their design life with under bonnet temperatures would max out at about 3 to 4 I reckon! Plus the fact that the diesels cant hit a battery hard makes it worse if your battery is a little weak and old.
