Quote Originally Posted by oj88 View Post
Draining a lead-acid battery, regardless of health, will reduce its lifespan. This reduction in service life seems exponential as the battery ages. In other words, a new battery will have better chance of being revived when discharged compared to another that's on its last legs.
my 3 year old battery flatlined because i left the domelights on, during a long-ish weekend. i could not revive it.

my 1 year old battery died, because the alternator malfunctioned. i had the car push-started, and after a year, the battery is still good.