Sounds like a bad cell in battery, had same problem with last 4 batteries i have replaced, Happens all at once no prior warning, just came out and battery is dead ,jump it and all is good shut it off and will restart right away but if you leave it set for longer time will be dead again.
Time for new battery!
Let us know what batteries you are buying! They must be pretty bad. I have one that is 7 years old in my Dart, and have a several cars where the batteries are 5-7 years old and doingn OK. The Dart battery gets disconnected if sitting for long.
Have you checked your battery voltage with the car warmed up and at fast idle to see if the system is over/undercharging them?
