That's one of the beauties of a turbine engine. If it starts and N1, N2 RPM and fuel flow is within spec, and you don't exhaust the fuel, the chance that that engine will run for another 5 hours is extremely high.

If my experiences with my own (single piston engined) airplane are in any way representative, I would be surprised if the first flight out of major maintenance isn't statistically significantly riskier than a random repo flight.