I use the "This rule has expired" remark to remind me of once off recordings that I have done, and may not have watched. If I see something I want to watch in the Guide, I tend to just click record and create a one time recording. I don't always remember everything I have done that for, and of course they are all then mixed in with existing recordings, particularly OTA movies. Of course I can just use the Recently Imported smartlists, but I'm not always looking, so the remark is a reminder.
Also, I do suspend recordings occasionally, and the remark is then automatically filled with "This rule is suspended until dd/mm/yyyy."