it's my long experience that it almost is never worthwhile to make a car rental reservation well in advance. The rental companies have no incentive to offer low rates or any deals way down the road. Each rental company has this little man in an inside office, he lives with his mother, and for the past 37 years he dutifully shows up each day at 9 am, with instructions to develop a rate structure for the next 21 days. Anything beyond that, he's ordered by the top to simply put in "standard" rates with no discount or incentive offered.

So although it's admirable you're trying to plan out your trip over Christmas, making a car rental reservation so far in advance is futile. I'd add a note to your calendar, to check 60 days in advance (a total waste of time to get a cheap rate but ya gotta start somewhere), then 45 days in advance, then 30 days in advance, then 15 days in advance, rebooking it if you find a lower rate or promotion.

Doing it now, however, is about as productive as voting for Budget as the friendliest car rental company around...you won't have much company or success...