I know I have a very very small draw on my 79 idget, also the alternator is not doing it's job perfectly by any stretch. If I don't start the car at least once a week in the summer, or twice a week in the winter it will not start.
I've worked around the issue by using a trickle charger when the car is parked at home. I also carry a jump box in the trunk for the rare occasion that it won't start when I'm out and about.
Interestingly, the one time I could not get it going while not at home was in the Costco parking lot. I went in, bought a new battery installed it and immediately returned the dead battery for the deposit. Talk about good timing!