Under normal circumstances I don't mark my queens. I have 6 hives (well technically 7 right now, but by tomorrow I'm pretty sure it'll be 6). It's rare that I don't inspect a particular hive once every 2 weeks, so I'd likely catch a supersedure if one was happening, and if I miss one, I don't really care that much. I'd rather have a supersedure that I didn't catch than accidentally injure a queen marking her. However I did mark a queen once, when I had a hive that was swarming itself to death, and a bunch of virgin queens were running around in the hive. I arbitrarily picked one queen to be the winner, marked her, and removed the rest. That way if I missed a queen, I'd know if the queen I was seeing was the winning queen or not. That actually did happen, but I never found the marked queen, so the two must have fought and the marked queen lost.