The best time to buy is when you can use your new rig. Let me explain:
Buying a new rig in the dead of winter then storing it until Spring unused is not a good idea.
>>You waste many months of warranty time.
>>You don't find out immediately what needs fixing and by the time you do, the dealer is harder to deal with for repairs.
Can't tell you how many times I have read about someone who bought a new rig, parked it for months on end. Then in the Spring, planned their trips, un-stored their rig and found lots of stuff that needed dealer attention to fix. Spring time, the dealer is busy and couldn't get to it....vacation ruined.