97 sentra distribtor problem

[twammy]

hi. i have a 97 sentra with the 1.6. i am on my third distributor in 6 months. it starts with the car skipping badly until the distributor fails. changing plugs, wires, cap, and rotor don't seem to affect the skipping. when i put a new distributor in it works great for a while then the pattern starts again. 220000 miles on it but i love my 40 miles to the gallon. help!