Here's the way it was explained to me by the diesel mechanic the installed the VP44 on the 2001 Dodge Cummins I used to own.

The VP44 uses the diesel fuel to lubricate and cool it's self.

When the lift pump gets weak it doesn't keep the flow required to cool and lubricate the VP44 injection pump.
Hence it burns up/wears out.

He also said to never have less than 1/3 of a tank of fuel during the hotter months for essentially the same reason.
He said that since it's getting some hot fuel recycled back to the tank after lubricating/cooling the VP44 pump with less than that in the tank it's harder for the fuel to cool/lubricate the pump.

Is what he said absolutely true?
That's a good question, but it kinda makes sense to me.

But that's why I'm looking at 12 valve Cummins Dodge trucks right now rather than a 24 valve with the VP44 injection pump.