I think that I've probably (nearly) killed it after ~3 years of daily cycling, and it's behaving distinctly ill today.
I'm tempted to upgrade to 100Ah if the space I have can take the physical load.
I should think that with some TLC this battery still has use beyond a doorstop, if not I'll eventually cart it off to our near-by recycling depot and pretend it's a car battery for simplicity.
Probably couldn't get a replacement to my door until after Christmas given ice up here, so no great hurry.
Any interest?
Rgds
Damon