Not necessary at that time of year unless you just can't stand standing in a few short lines. I get it whenever I can just to have but that's just me. Not really required if you are there a couple of days or more in a slow time like early December
No need to buy in advance either, if you get there and feel you need it you can buy on the spot. Remember that the one you buy is a one time use type, what you get when you stay onsite is unlimited at locations that accept express.