I didn't buy the big batt, I bought the 545, and got it "walk in" locally at a battery store here.
I got to look at the date code on the box before purchase, it was within the month of purchase, so I was pleased.
at the time they had a 5 yr warranty, and a typical 8 year proposed life based on duty cycle.
this is from the site:
Constant voltage portable charger parameters:
Standby, per 12V battery 13.5-13.8V no current limit required
Cyclic, per 12V battery (16-hour recharge) 14.4-14.8V no current limit required
Typical deep-cycle life at 25°C/77°F
at a 5-hour rate 400 cycles at 80% DOD
Typical service life at 25°C/77°F Medium to heavy duty usage – 3+ years
Light duty usage – 5+ years
I suppose it's out of warranty, but if you can find someplace and do a walk in purchase, saving the postage, I'd suggest another one.