How long is a piece of string?

A built Group N engine with output around 140-150kw atw with 500nM of torque, running Elf WRF fuel, 24-26psi boost with a shitload of timing will last around 3 rallies, about 600-700km, before it starts feeling tired. Engine will be down on power at that point and likely hood of engine failure increases dramatically after that. This is also with a rev limit of only 5000rpm as revving it any harder is pointless with the 32mm restrictor Group N cars have to run.

End of the day it all comes to how hard you drive the car, how highly tuned the engine is and how lucky you are.