If you made the starter from White Labs, WyYeast, or similar, then I'd put it in the fridge to settle. On brew day, you can pour off most of the clear liquid, and then pitch the slurry.
If you made the starter from a very small starter, or if you are brewing a large beer (either in volume or gravity), then you may want to step up the starter to increase the cell count.
With the stir plate, you really only need 16 - 24 hours for most brews. Add another 24 hours for each step if you need to step it up.