Gents - I'll look into Morganatica. Does anyone know how to upload a .pdf document to this forum? I have a scanned copy of an article that is pretty good on lead-acid batteries.

Bodger - depends on definition of life..........most people would say failure is failure to start the engine, which is very much temperature dependent. Also, one bad experience requiring a jump-start may get you through another year when it warms up!
I'd say 6-10 years life is average, so you were unlucky with the Sebring, and lucky with the Mog........there are so many variables with conditions of use, and remember the car battery is really only a capacitor that fires up the engine - the alternator supplies the power when you are driving. That's why vehicle SLI batteries are so different to 'marine' deep-cycle storage batteries. It's also why you'll find politicians and journalists don't know the difference between energy and power.....now don't get me started (groan)........