Two (or was it three) years ago I had 24080 Airmiles, and got a letter saying that because of the lack of activity on my account they would be cancelled in six months. Went on the website and lo - 24000 bought a First Class return ticket (no cash needed) to HKG, and my dates in June (when no one in their right mind wants to visit except me) were available. I let the 80 miles go....
Moral - if you want to travel when everyone else does, you have no chance of availability. If you are willing to go when no one else wants to then it is usually not a problem. Flexibility is the key.