After spending most of the day looking, I think I've found the problem.

We update products in two groups: those people are tracking, and those people are not; the former updates 3-4 times per day and the latter about once a week. When someone tracks a product that was formerly not tracked, it currently takes one full processing session of the "not tracked" products to get this product moved over to the "tracked" group of products.

I believe this explains why your products, although tracked, haven't gotten updated since you tracked them. The fix is to make sure products get moved to the appropriate group right when you create price watches for them, which ensures said products will get updated every day rather than every week.

We're still confirming that this is indeed the cause of the problem, but, since this is a good change to make anyway, I have implemented a fix already and we will launch it once it is fully tested.

Hopefully this will keep tracked products much more fresh in the future! Does the explanation make sense? The gist is that your products should be updated within a few hours and will be updated 3-4 times per day thereafter. And after testing, we'll launch a change to help us avoid this situation in the future.