How long to charge 18 volt charger?

The battery itself should last almost indefinitely, although the charge on it won't.

That depends what you use it for. If you load it lightly or not at all, such as leaving

it on the shelf, it will last quite a long time. Whereas if you load it heavily, such as

to energize a parallel bank of high-intensity incandescent lights, the life of the

charge on the battery will be comparatively much shorter.