I like seeing what's happening in town, so I set up a task to check various local events listing—e.g., “Check Museum of Contemporary Art’s events calendar". I made each of these repeating tasks, but since these listings aren't updated at predictable intervals, I was struggling with how to make this work.

I'd check an events listing, note the latest date that it covered, mark the task complete in RTM, and then change the due date of the new occurrence to that latest date from the listing (or shortly before), so I'd be prompted to check back then. This worked pretty well, but depending on the Smart List I was looking at, the new occurrence often wouldn't show up and I'd have to change views to find it.

So here's what I finally figured out: I set each task to repeat "after 1 day" and tagged them "repeatwhen". Then I added the following to the end of each of my Smart Lists: "OR (tag:repeatwhen AND added:today AND due:tomorrow)". Now when I've read all the events on a calendar, I mark that task complete, and the new occurence pops right up for me to set the new due date.