I've one some 5 years old. Showing signs of failing - must check for bike discharging the battery first to confirm.
If it is at the end of its life I'll buy another one.
It has been discharged totally flat once some 2 years ago for about 2 weeks (broken leg and collar bone) ... battery recoverd. Discharged over night (ferry crossing) - recovered.
Higher cranking speed than standard battery.
Regards Frank Warner
motorcycles BMW R80 G/S 1981, BMW K11LT 1993, BMW K75 G/S