This happened to me in 2005, I reached my gold tier membership requirement early and MPC will not reset my miles until I reach the membership anniversary date. I ended up finishing my membership year with approx 75K miles. In 2006, I didn't need to travel as much and I ended up completing the membership year with about 10K short of retaining my gold status so I asked MPC to review my 15K credit from 2005 as part of the renewal calculation. They approved the request within minutes and renewed my gold membership. I don't think they will allow you to roll the credit over for more than one year but if you're are 20K short from reaching the Diamond tier then I reckon MPC will grant you the membership