I have one of the AGM (Absorbed Glass Mat) group 27 Restoration Batteries. I'm Pretty sure this battery is 15 years old. I could not find he receipt, but I know it was done during that last part of the restoration. (drive 2500 miles a year mostly in summer)

It as never failed me and starts and cranks strong every time up to this point.

when I was reinstalling the radiator I must have bumped the negative battery cable and it was brittle apparently it was almost broken off, but I couldn't see the break. I tried to crank the car over multiple times and finally it drained all the juice. When I went to inspect the cable connections again it just broke off in my hands.

I put new + and - cables. Jumped the battery drove around a little. 15 min later it wouldn't start.

jumped it and took it over to my mechanic. He said it was the voltage regulator. Got a new one, jumped the battery and drove it home. 15 min later it is dead again. Mechanic said the battery appears to not be holding a charger. But...

Charged it for an hour yesterday with a battery charger. Started up and drive great yesterday. 3 times both hot and cold. Took it on several short trips today and a 10 mile drive.

It started several times both hot and cold. Seemed to charge up right a way (dash amp meter) and not discharging to any degree.

A new one of these Turbo start batteries is $320 from Remy.
Am I just fooling myself to think it will last a little longer? Am I just running of the charge from the battery charger and it will crap out in a couple of days?

Thanks! (sorry this is long)