I usually just go by how I feel. If the ol' dome feels dry at night I'll apply a bit of moisturiser.Red
I moisturize after shaving, but that's it. I have a naturally oily skin, so there is never a chance my head will dry out after the initial 'after shave' lotion.
Actually a cheaper trick is to take a wet paper towel at work and wipe the whole head... may sound strange but does a reasonably good job of cutting down on the grease/shine... AND free.