6.5 years on a battery - new personal record!

I had a Delco battery that I bought used in my Ventura that lasted me 13 years, I finally had to replace it at the start of the summer this year. I have no idea how old it was when I got it, I never disconnected it over the winter, never had a trickle charger on it, nothing. It would always start the car after sitting all winter in my unheated garage. I think I paid $40.00 when I bought it.