2015 Xterra Pro-4X
I carry a spare crankshaft position sensor for the Gen 2. Fairly easy fix and it's ugly when they go bad.If you're reasonably sure that 6 new coils are working, then by the same reasonableness you should be able to expect those to run 200,ooo miles as well. Driving around with extra parts that aren't likely to be needed spends money and uses space, things that could be put to better use.
If you subscribe to the idea of having spare coils, then spare spark plugs and a couple of injectors might also be on the list, as well as other things. But where do you draw the line?
It's up to you.