Last time I did the mags for miles. However, now I do something to keep my miles current. I linked to the AA dining plan, so I very occasionally happen to eat at a restaurant linked to this (we rarely eat out). I've completed a couple applications for insurance, etc so that I can get free miles. I'd look and see if there is anything for your carrier where you could earn miles before I spent them. However, if they're expiring quickly, the earned miles might not post in time. In that case, I'd just spend some.
Good luck,
Jennifer