Yesterdays Starlink launch (F9, from LC39A, landing on ASOG) re-used a pair of fairings. One was on its 4th flight and the other half on its 5th. That is pretty good news. Sure they are not VERY expensive, but now that launch costs are below $50 million, the fairings $6 million cost starts to matter a lot more than on say a $133 million CRS mission. (I know, no fairing on Dragon, but you get my point).

And they should be regularly serviced and extended by the astronauts.

So they could work indefinitely long.

I see nearly zero benefit in the L2 placement of the JWST and having the last JWST photo from the Ariane second stage is imho hilarious.