Please excuse my limited knowledge since it's been a while since I played. If memory serves you could have a WeakAura show after a set amount of time, think it would be an invert toggle under the WA's display settings, then set the custom trigger to hide after a duration; though these might conflict with one another. Though in my attempt to relearn WA I came across a possible solution.
http://i.imgur.com/GZ6NpDC.png