Serp belt is good to have a spare, I think, but since those have been standard issue now for the last what 25 years, I have yet to see a serpentine belt break unless it was destroyed due to failure of another component. I carry a spare in the Dodge truck just because I've had to replace the belt due to squeaking. But anymore, it's not on my maint list.
At 75k miles I wouldn't expect problems with pretty much anything. We have a fleet of older GM gas pickemups. All 6.0s and all abused and never really any engine or drivetrain issues. Brakes, unit hearings, u joints that kind of stuff on 100-175k mile trucks.