This comes down to how much freezing weather your rig will be exposed to...
Since I'm overly cautious: I'd drain and winterize everything. frozen pipes can be your worst nightmare!
It's not just whether or not your tanks are heated: it's also about the plumbing underneath the rig. Is that also protected???
Also: you definitely want to add some fuel stabilizer to the fuel.
(Or park it at a lower elevation that stays a bit warmer...