I got almost 10 years out of one, 7 so far on another.
I usually get 5-7 years out of any battery - except ones I bought from WalMart, those either leaked or died within a year - as I put trickle chargers on them, but I use the Optimas for cars where I want no chance of any damage from terminal corrosion or acid.
Schumacher has a trickle charger that also works on AGM, and I saw the other day that Duralast (AutoZone) also sells one. Usually around $28.