If a car is not driven with any amount of regularity does the magneto discharge? Or could I expect it to function the auto regardless of drive times and frequency.
It shouldn't discharge from sitting regardless of the length of time.
I have an unrestored 1917 roadster and the mag works fine. I'm pretty sure the only time the magnets were charged was when it was assembled in 1917.
Driving the car will not charge or discharge the magneto. Only time will cause it to discharge, but it will take years to do so.
There's one exception:
If through fiddling around or because of a faulty ignition switch, positive juice is fed to the magneto terminal, it can almost instantly discharge the magnets.
But then, they can be re-charged by doing the same in reverse. Instructions can be found on this Forum.