Good question, not sure on the answer, but I certainly would not try it. You have no intention on taking the flight, and this can be considered tampering with the inventory. Not sure how their IT system will deal with this, on face, 2 transactions will take place, the award booking, and then the miles deposit, pushing the clock forward 18 months. You also forget that you have to pay to have your miles reinstated, I presume you have no status if no activity within the past 18 month or so. There are cheaper options out there, already mentioned.