I would note that depending on the whims of the system, you might not be able to find the award space again after you refund your ticket, since Lifemiles availability fluctuates more often than the seasons change, and they might block a different partner’s awards from one day to the next, I would not count on them being the same in the months between when I booked the tickets and when (I find out that) my flights have been cancelled. My advice is check before you cancel. It can definitely save you time, but you may never see that beautiful itinerary you crafted to perfection ever again, because having the stars aligned still won’t guarantee you that Lifemiles is aligned with Starnet.