i used to have a 4yr old batt that my dad hadn't changed on the car, so when i got it, i had to drive it everyday. Previously he commuted to work everyday with it so it still lasted for the next day to start it. I still managed to start the car, when after 3 days, it had dropped to a voltage of less than 10 volts. Amazingly, i still started it up. This happened quite a few times. Then i finally convinced him that batteries should definitely last more than 3 days and more like 2 weeks or so. I replaced it with a Energizer batt wit 500 cca and 80 rc minutes.
I would of tried to reconditioning the batts if i would have known how to.
oo and for testing the battery, you should find the internal resistance: you measure the voltage of the charged battery without a load. then you add a load and measure the amps of the load and the voltage of the battery With the load. Then you find the difference of voltages of no-load and loaded battery, then divide the difference by the amount of amps of load you put on. the equation is: R = (Voc - Vl ) /amps
it should be something around a few miliohms but i dont know how many ohms is considered "bad".