Two things - the first JetBlue planes were leased and although I don't know the terms of the leases, I'm quite certain they are long-term. The first a/c to fly for JetBlue was N503JB.
The first owned aircraft by JetBlue is N507JB, which will soon be celebrating its 4 year birthday (of being in-service). Considering N503JB saw its first revenue flight in Feb. 2000, I'm sure all of these planes will be in service with JetBlue for a long long time barring write-offs.
As for JetBlue getting their planes for free, that is absurd. There are literally a dozen posts about this "myth" on airliners.net but I am quite positive B6
is paying for their planes. Granted the price was probably good and attractive to JetBlue but then kudos for them for nailing a good deal. I'm sure ordering 100 at a time gives you a pretty good discount! I doubt the deals were setup so that B6
pays less now and more later - Airbus is in this to make a profit to and probably couldn't afford that risk! Let's be realistic, people!