@Cybertronica
You'd want to run a buff test as part of your Test Conditions. The one you're looking for is:
MoodBuff_Hidden_Asleep
In setting up the moodlet itself, set the emotion weight and duration. Check the "Ignore if the Sim Already Has the Buff" (or you can uncheck it, it probably doesn't matter, although this will likely cause the moodlet itself to blink a bit). As a continuous loot, the trait will be checking every 10 in-game minutes to see if the Sim still has the buff (in this case, whether or not the sim is sleeping), and will stop "refreshing" itself once the Sim wakes up, but the moodlet itself will remain for whatever extra duration there is after the Sim no longer meets the test condition.
