Some people wax it before each session, some other every now and then. And some never.
I personally do it on a regular basis (every couple of sessions or so). If you care about your board and want to preserve its base, it's common sense really. In any case, it can't hurt to wax it often.
As far as storage goes, it is recommended to store it waxed, flat, in a dry environment. If you've only used it twice, you probably still have some wax left in the base, but I highly doubt it fully covers the edges.
If you're into snowboarding, get yourself a waxing kit. You may even get some pleasure doing it. Or not.