From what I've read, the pump is cooled by fuel in the tank and it's the heat caused by running the pump while low on fuel that kills it. So I guess if you idled the truck a lot while it was low on fuel it would eventually kill the pump.

 

I've heard that the pump actually sits in a little resevoir, and it sucks fuel into the resevoir, and then pumps it to the truck, so it's pretty much always cooled by fuel... unless you're running on fumes, lol.

 

When I changed the fuel pump a few weeks ago I did see that it pulled fuel from a white plastic tray/resevoir type thing inside the tank. However, I think that if the fuel level was low (to the point that parts of the fuel pump filter is not submerged in fuel), the pump will start pulling air. This causes the pump to work harder to deliver the same volume of fuel to the engine and the pump will also not be cooled as effectively.

This might not be the case with the newer gen blazers, but from what I saw on my tank and from talking to technicians, it does happen with my gen Blazer and is one of the causes of premature pump failure.