Odyssey EXtreme PC110 ... Any experience of one failing ???

[glow worm]

I've had my very expensive Odysssey Racing battery in my Chim for 3 years and no problems. I just wondered if anyone has had one fail by now, I know the bumf says they last twice as long as a normal battery but I wondered if anyone could validate it by experience . Also if and when one does fail , does it give you any warning like not holding the charge very well or do they just go dead if a cell fails ?
My experience of modern convention batteries is that you get very little warning , one minute working then dead , since I guess the plates are so thin these days they just turn to powder. Anyone got any thoughts ??? Because they are so small . I was thinking of investing in a spare to carry in the car just in case. I already carry a SNAP-ON Power Booster pack but I was told I could knacker it running the car on it ( but I am a little paranoid) .