JetBlue just extended their schedule to allow you to book flights through April 30, 2019. While most larger airlines allow you to book travel 330 days in advance, JetBlue extends their reservations systems a few months at a time. Up until now you could only book through February 13th so this means you can now book for Presidents Day weekend, February Break, Spring Break, etc.! Flights during those peak peak times will most likely be the cheapest today!
I know booking this far ahead of time is nerve racking as you do not want to book a flight and then have to change or cancel it – and those fees are not cheap! However, if you have JetBlue Mosaic status, you can always cancel and rebook your flight for no fee. Also for all other passengers, if your flight goes down in the next 5 days, you can get a credit for the price difference.