2001 Dodge Intrepid oil sending unit

I have a Dodge Intrepid 2001 2.7L engine and over the past year I have replaced the oil sending unit 3 times. The first time my oil light was flickering and let me know there was a problem. Bad oil sensor, so I had it replaced. About 9 months later, oil light came on and there was no oil registering on the dipstick. Oil sending unit was leaking. Replaced it. Just this week, decided to be cautious and checked oil and there was no oil on dipstick. Check oil sending unit and once again it is leaking. Replaced again. What could cause this unit to repeatedly start to leak/ go bad? I would not think that I bought 2 defective parts. Any ideas? I religously have the oil changed every 3000 miles and when there has been a problem it happens at about 2000 miles.