I have never used the automobile ones, but I have used the marine deep cycle
ones and they do last longer under rough conditions than conventional
batteries.

On the other hand, for what they cost, I think you're still paying less
per month of use by purchasing an oversized conventional battery.
--scott

They last 'pretty' good, but still up and die like regular batteries if
used off road.  One of mine lasted until it's 'very' short warranty was
'just' up, then a cell died and I was out a battery.  The other that I
don't use off road has lasted about 7 years on an occasional driver so far.

For off road I am going to stick to the chain store batteries with their
5 year warranty so at least when a cell goes bad from vibration I can
just go to the nearest chain store and replace it 'free'.

I got suckered into their hype as an indestructible battery.  As usual
the hype was pure bullshit.

Just my $0.02,

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos:  Non members can still view!
Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590
(More Off Road album links at bottom of the view page)

I like them. They seem to outlast conventional batteries by about 2-3
years, and since they don't outgas at all they don't cause nearly as
much incidental corrosion (none, in fact). They also don't
self-discharge so I can start my stored cars after sitting 6 months
without pre-charging the battery.

They are overpriced, though. Not a winner if battery LIFE is all that
you measure by.