Originally Posted by Eendracht

However, I believe your membership ends when you do not fly KLM for a whole calendar year:

2004: You make 60 flights and become PE
2005: You are PE, but you make no flights
2006: Your membership is cancelled as you made no (qualifying!!) flights

Maybe you have to 'fall down' to Blue first, before this rule is enforced

2004: You make 60 flights and become PE
2005: You are PE, but you make no flights
2006: You become GE (you fall down one level), and again you make no flights
2007: You become SE (you fall down one level again), and again you make no flights
2008: You become Blue (you fall down one level again), and again you make no flights
2009: Your membership is cancelled.

Note that low fare flights are not always Miles/'flights'-earning any more. So making one cheap 'milage run' will not ensure your membership for another year.