> But the engines have a lifespan measured in hours
I think it's slightly more correct to say that they have a service interval measured in hours. The jetcat ones require service every 25h of use, but there are other companies that require service less frequently, although the highest interval I found is 100h.
For common hobby grade engines that is correct. We actually have working one on one with a manufacturer for over 8 years. Over this time we have gone through many iterations to make the engines rated for manned flight. So we own the special internal components that make these much much better than hobby grade engines.
I think it's slightly more correct to say that they have a service interval measured in hours. The jetcat ones require service every 25h of use, but there are other companies that require service less frequently, although the highest interval I found is 100h.