Originally Posted by
tankgirl
Anne, others here have said that either the SuperCell reps or mods have admitted that inactives are either pulled from matchmaking or pushed to later in the queue, but I haven't found that post myself. Several people on the forums have noticed that when they go inactive (usually with a second account) and come back on a week or two later, their log only shows attacks during the first couple of days. At this point, both of these points are circumstantial evidence, but hopefully someone else here has more concrete information (e.g., link to the rep/mod post).
Based on the reports of people who have gone inactive, SC's definition seems to be based on how long since the last log-in, and it's on the order of a few days.