Slaanesh is the god of excess, but there's rules to the matter. Sleeping 16 hours in a days won't feed her, even if it's excessive. Sleeping 16 hours a day every day for years wouldn't do anything either on its own.
However, if someone craved that kind of sleep, indulged that desire by ensuring it, felt strong pleasure every time their achieved that sleep, slowly allowing this manner of excessive sleep to become an obsession, for weeks, months, years at a time, then yes, Slaanesh would probably notice.
While anything can be taken to excess, there are rules to it to actually invoke Slaanesh and feed her, particularly involving the "overindulgence of desire" because the sensations around that are what she actually feeds on and notices.
Notice in the Khorne's Cup story, which I mentioned in the other post, that it is their "drive for excess" and not excess itself. Drive, desire.
Likewise, the 6E daemon codex, page 16,
>He is the God of Obsession, the Master of Excess in All Things, from gluttony to lust to megalomania. Wherever mortals are ruled by their own unquenchable desires, the Dark Prince is there in the shadows, whispering, tempting, and feasting on a banquet of souls.
It's not "whenever a mortal does something in excess" or "whenever something happens in excess", it is
>ruled by their own unquenchable desires
That is what takes them to excess, that it was feeds Slaanesh. And yes, it can be anything, but it is not excess itself but the gratification one feels around indulging in it.