I'm renting for 10 days in January (18-28), but I have to say, it's way too early to worry about high prices. Yes, it's good to monitor, but don't panic. I just returned last weekend and my price on National did not drop until 4 days before my departure. I took a peek at my previous January rentals and I've always managed to get great prices for January.
2011 14 day rental total $232
2010 10 day rental total $152
I've rented this year in January, May, August, and October and I've found the rates to stay high until just weeks prior. As long as you have a Saturday night stay and not renting during the holiday weekend, we/you should see some decent rates.