The question perhaps is: is anyone else any better. Modern jet engines are amazing technology and really do push the limits of design and material science and there are trade offs being made all over the place. They are also wildly expensive so while there are "spare" engines there aren't lots of them. There is one slight issue on the horizon which is the rate of shut-downs. At the moment it seems low enough but if the rate increases not only do you have more aircraft/engines waiting for repair but over certain rates the authorities don't like the aircraft going too far from land.

For interest as a comparator the A380 that had the huge engine failure in Canada, powered by an "Engine Alliance" Gp7200 has only now got a spare engine. That's over two months with it sat there waiting for an engine.

There are about 520 GP7200 engines in service. For RR there are about 500-600 Trent 1000s in service.