Is there any way to predict when I'll get an e-mail from JetBlue on some apparently random day, announcing a fare sale for travel purchased only on that day, for travel on what seems like relatively short notice?

I understand this can work very well for people looking for a quick getaway anywhere they can find a cheaper ticket. But this can be a problem for people who are planning a more complicated vacation in advance. Do I buy the airfare now and lock in my other travel plans, or wait? If I wait, hotels, car rentals, and other vendors' inventories will likely decrease, and their prices may rise. JetBlue may or may not decide to drop their price, and it may or may not work for my travel dates. If the price does drop, JetBlue will issue a travel credit, but that may or may not work well with my travel plans in the future.