I checked mine at 10,000 mi and it was low 1/2 bottle.
It only takes 2 bottles to fill it.
Now I know where the intermittent oil puddle came from. It seems that with some new superchargers, the seals take a little time to wear in so pressure can blow some oil out of the pulley nut breather vent.
My service manual recommends checking it every 30,000 mi but no recommendation on replacing or flushing it all.
This oil runs very hot, reaching temps of 180 - 200 F.
I would recommend checking it every 10,000 mi.....it'* so easy to do.. and topping it up to the bottom of the plug threads. It certainly wouldn't hurt to suck a little out and replenish it with clean oil to keep the additives up to spec.