I suggest spend some time searching the net as lots of Synthetic polish on the market now that will out perform old school wax.

I have never found a wax that will last at most a few moths if the car lives outside.

At a minimum I would polish both spring and fall. New high tech polish is much easer than the old school stuff from years back and if you apply it often or before the car needs it... its almost wipe on wipe off.