Fuel level has little to no effect on fuel pump life, this is a total urban myth.
Most electric fuel pumps are DC brush motors and have bushings. Think of it like a starter motor. The brushes, commutator and bushings wear out over time.
Most pumps last about 5000 hours. Its not a mileage thing, every second the engine is running, so is the fuel pump, so if you live in a congested area the mileage will be much less for the same amount of run hours.
If you do not want to be stranded, replace the fuel pump around the trucks 10th birthday.
I have not really searched for the typical lifespan on these pumps, some may fail earlier, some may fail later, but fuel level does not adversely impact pump lifespan as there is always fuel running through the pump.
Since I assume you have to pull the tank to replace the pump, best to replace the pump on "your" schedule than the "trucks" schedule. This way you can run the tank very low because dealing with 20+ gallons of fuel is no fun.