Mid-to-end of January has always been a good time to go.
Probably one of the few "slow" times.
One of the few remaining "value" times for resort hotels, everyone back in school, it's cold (relatively), holidays are over, a lot of stuff is closed for refurb, families just spent a lot of vacation time or money on Christmas, etc.
But between the Pro Bowl, Marathons and other things, this window is narrowing more and more.