Well, it's 7 years old, and I got a LOT of use out of it. I'd been charging it every few months to keep it from getting sulfated, and I just realized I hadn't had it out to use, or charge, in about a year.
It *might* come back if I get a different charger that will whack it with high-current pulses, but in my experience, while it might come back, you'll never get anywhere near full capacity out of it.
Lesson learned (actually, lesson remembered): CHARGE the damn thing on a regular basis!
I'll put it in the car, and exchange it for a new one on the way home from setting things up today.