[hoseja]

The raptor burns highly purified methalox for a couple minutes at most. The ship engines have to work for weeks and years economically running on bunker fuel. From fundamental thermodynamics, the bigger an engine is the more efficient it is but you obviously need to compromise on that in a rocket.

[avmich]

Soyuz rocket takes 9 minutes to get to orbit. Raptors are multiple-use engines, their lifetimes could be hours of work, which is a lot for rocket engines. However it could be possible to increase lifetimes at least another order of magnitude - an NK-33 engine once run uninterrupted for 14 thousands seconds. Consumed a lot of kerosene.

RL-10 can avoid too big stresses, at least not heating to high temperatures, so this is another hint on possibly long working rocket engines...