Hi,
Have you read the changes introduced to the FB program starting April 1st? An ideal date because the program has become a joke. All fare except fully-flexible economy will yield from 25% to 75% miles, which is a huge hit for most coach traveller, and the redemption level willl be upped greatly, except for coach.
The only persons not impacted will be customers who mostly fly full-fare economy and who redeem in coach award. If you're not in this category, I urge you to read the dedicated thread in the Flying Blue forum to see how it could impact you before deciding to stay with FB.