By the way, I once heard that condition of F-22 stealth coatings becomes "critical" after 1,7 h of flight or so; it doesn't sound very optimistic, does it?
Entirely possible. The B-2 IIRC has had issues with its radar absorbent paint being stripped off if flying through even just rain clouds at one point. However, since the F-22 has been cancelled I doubt it'll be an issue, unless the same problem occurs with the F-35.
The F-22 hasn't been cancelled, only fewer than expected/planned were built due to budget constraints (instead of more than 600, "only" 195 were actually built).
The F-35 has a very different stealth coating "system" compared to all previous Stealth aircraft (F-22 included).
Instead of relying on radar absorbent paint which indeed has issues in terms of maintenance, the F-35 uses a rubber-style skin/coating which is not only much more resistant (than the radar absorbent paint) and therefore it lasts much longer but it's also much easier and cheaper to repair (in case the coating suffers some sort of a rupture or fracture).
