How often does the water pump have to be replaced?

i had to replace primary water pump at about 49300 miles. i believe that is way to early for any vehicle especially german technology. brake pads and rotors had to be replaced at 30000 miles. that too is not good for any low mileage vehicle.had to replace alternator at 49900 miles due bearing grease slinging out. was advised to replace pulley but the cost was cheaper to replace the whole unit and serpentine belt at same time. nothing cheap about owning an audi.