With our last car, we would drive it, let it sit for 10 days, drive it, let it sit for a week.
One day, the battery was dead. The doors automatically locked.
After the second occurrence, and even though people told us this was not necessary, we simply moved the Battery Tender from the Harley to the car.
My understanding is that devices such as Battery Tender will extend the life of a battery.
In either case, it was great to know that the car would always start.
(However, try to remember that to unplug the unit from the car...er...it is rumored that someone forgot one time...just a rumor).
- doc