As someone who did 39 flights in 3 months last year using JetBlue's Bluepass[1] I'd LOVE a lifetime unlimited pass. It's pretty clear the prices they were charging were far too low, especially for first class.
If I had an unlimited pass I'd probably average 2-4 flights per week, many international. It's even more practical when you have unlimited access to their lounge. Take a red eye and shower at the lounge and you just saved a day of hotel expenses.