I have a similar tank that I bought perhaps 15 years ago. It holds
pressure indefinitely, and I've never found water in it. (Checked once
about two years ago). Most of the atmospheric water vapor will be
compressed out in the compressor's tank.
One thing to be concerned with is this: Don't fill it to its limit when
it's very cold outside. Leave perhaps a 20 psi safety gap. Once it
warms up, the pressure in that little tank will increase, just like
anything else -- car tires, basketballs, etcetera.