I don't think finance rates for Subies have an identifiable pattern of up and down fluctuation. Though, wouldn't it be cool to know how and when the banks decide to fluctuate the finance rate? That freakin rate depends on a lot of different factors, the main one being the bank.
Of course, you could always finance through your own bank instead of the stealer's. You "might" get a better rate.
That said, IMO, 2.9% is pretty darn good, especially given the popularity of the new models. Sure, it isn't is as good as 1.9% (I've seen it), which you can get from time to time (who knows when). But I don't think you'll EVER get 0% financing on Subies (I've never seen it). They simply move too quickly.
In my neck of the woods, the finance rates are set by the stealer's partner bank (Chase), and the bank DOES NOT budge, no matter how good your credit score is.
My credit score is impeccable, and I couldn't get my stealer to even consider doing anything with the finance rate. My sales guys said, "it's been set and that's it." Period. He had no say in the matter. So, I settled for 4.9%. Man on man, I wish I had 2.9% financing.
Thankfully, I didn't have to finance a whole lot. That's my .02