make sure when the switch closes, the contacts are even, you should see a bar with 2 contacts on each side of the pressure switch. if one is tweaked or not square, it can cause premature wear.
check your amps when it turns on and when its running. you could be drawing high amps during start which can cause premature wear. usually caused by voltage drop, (at the switch, wire nut in the well loose breaker etc) or even a motor that is starting to go bad. but thats the worst case scenario and i wouldnt jump to that conclusion.
i bet its not mating square, bent or tweaked spring or whatever.
turn off the power, verify its dead, and clean them up and run it. use a file or sand paper to just clean them up/take of little material off, press it closed by hand and see if there is high spots etc, make it mate square and even, you dont need to take alot off, its silver, so itll file easy and fast. just a c hair can make the difference.