This happens all over. A couple state parks in Connecticut that are right on the water have people who seem to be able to stay there all summer, but there is a two week maximum. I have heard that they trade sites with friends - they only stay for two weeks at one site, then switch. I don't know for sure, only what I've heard.
The state parks seem to try to combat this by changing the reservation rules every few years, but people always seem to find ways around them.
It may be "following the rules", but it prevents the majority of people from enjoying prime campsites in the park.