What is the life expectancy for a fuel pump for a VW Passat?

A few years to a couple of decades. It varies. How much is the car driven? Is the fuel filter replaced regularly? Has the tank been kept clean and moisture free (either by keeping it full or by adding some kind of additive that removes moisture, or by adding a fuel additive every several thousand miles)? There are some other variables that might been considered, but these are probably the main ones. Most vehicle fuels in "modern" countries are kept free of moisture and are filtered at the pump to provide motorists a clean product. If you've a moment while topping off next time you go in, why not ask them how they do that? They should be able to tell you.