"JWST needs to use propellant to maintain its halo orbit around L2, which provides an upper limit to its designed lifetime, and it is being designed to carry enough for ten years. The planned five year science mission begins after a 6-month commissioning phase. An L2 orbit is only meta-stable, so it requires orbital station-keeping, or the telescope will drift away from this orbital configuration." [0]

There's no mention of lifetime for the cryocooler @ [1], but if that thing becomes ineffective for whatever reason (helium refrigerant leak?), I think the telescope becomes somewhat useless.

[0] https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Lau...

[1] https://en.wikipedia.org/wiki/MIRI_(Mid-Infrared_Instrument)...