I drain mine periodically - if by "drain", you mean draining out the water
from the tank. *Always at the beginning of a paint job, periodically when
using my air tools. *I keep saying I'm going to install a sniffer system to
blow it off every time it cycles, to prevent water build up, but so far I
haven't done so. *As for simply draining the pressure off (if that's what
you mean...), don't bother. *No point at all in doing that. *My compressor
stays charged 100% of the time.

I was referring to the pressure. The tank has a small drain valve at
the bottom - I'm guessing that I can just crack that open every day or
two to let out whatever condensation builds up. I just didn't know if
it was OK to leave the tank under pressure for a few days to a week
between uses.