I've had a few of my fleet trucks go 300k+ with few problems. I tend to trade out around 200-250k unless the driver just wants to keep the particular vehicle for a while longer.
At 100k, I normally make sure the following are done:
1) New air filter
2) Transmission fluid and filter, change out stock boost valve for sonnax .490"
3) Front and rear differential oil changed
4) Brakes. Replace if low, flush system with new brake fluid.
5) New fuel filter
6) New spark plugs and wires
7) New PCV valve (some late models are sealed, PITA to replace)
8) Remove and clean throttle body (the ETC version can get rather dirty)
9) Clean radiator
10) Remove, lube, and/or replace steering shaft (intermediate shaft)
Around 150k, if it hasn't gone out already, I go ahead and put in a new OEM fuel pump. You can expect the stock water pump to go out around 150-180k miles, as well as needing new brakes (I go ahead and replace all rotors also just for peace of mind). By 200k you will be looking at a new alternator, fan clutch (04-older models) AC compressor, one or more wheel bearings, maybe a U-joint or half-shaft (4x4s), and various other things like window motors, side mirror motors, heated seat elements, various switches, and maybe a stepper motor in the gauge cluster.
At around 200-250k things like the transmission, axles, emissions equipment, suspension components and bushings, door lock assemblies and seals, and such will start going out.
Again, these are fleet vehicles I'm talking about. Personal vehicles that aren't beat on should go beyond 200k with few problems.
