That may be one for the "Guiness Book ....." Five years is a long time for little batteries.

I have a 1995 John Deere 30" rear engine rider model.
It's a Seras Die Hard Gold battery that is going into it's 7th season and still is strong.
I've read the normal lifespan of tractor batteries is 4 to 5 years but I think it's how they are strored in colder climates that shortens the life. I remove my battery in late fall, put a full charge with a battery charger then store it in my heated basement. I think storing in cold temperatures shortens the life. I've also read if storing on concrete a piece of wood should be placed underneath it.

When cutting season arrives, I charge it again with my battery charger and install it in the rider. Whenever replacing a battery, I try to buy one with the greatest cold cranking amps, you get what you pay for. Some say the greater the cold cranking amps the lower the life span, I don't find that to be true.

I leave it connected in the tractor which is stored in my unheated shed all winter. The one thing I do every winter is wait for a little break in the fridged temps and start/run the tractor for 15 minutes or so...typically once a winter in the February timeframe. I do this for two reasons: A) Run fresh (stabilized) fuel through the carb B) Charge the battery.

This is the original "JD" no maintenance battery. I have never cranked it down low at all. I've always maintained the machine well and it starts easily so the battery has had an easy life from that standpoint.