The difference between the F-18 and the F-35 is that while the F-18 might need extended maintenance after prolonged (read : more than a minute) supersonic flight, the F-35 may suffer catastrophic coating degradation that may be fatal in the same flight.

As for other operational fighters, the Dassault Rafale can supercruise indefinitely the Gripen indefinitely at Mach 1.3, the Eurofighter indefinitely at Mach 1.8, the Sukhoi-35 can if outfitted with the AL-41F-1S (meaning, some operational Su-35s can supercruise indefinitely, but not all). The F-22 is far from the only one.