4-5 hours on a stir plate is pretty good. Presuming your yeast vial is reasonably fresh, you can often be at or near high krausen in 4-5 hours on a stir plate, and pitching at high krausen is typically a good thing. I don't think it's necessary -- if you're really tight on time you'll be fine if you don't do a starter. But it can't hurt & could help to make a starter, even for 4-5 hours, so if you've got the time . . .
Currently On Draft: Bamberger Rauch Dunkel, Belgian Blond, Pilsener Urquell clone, Smoked Porter
Bottled: Concord Pyment, Mi'Apa Sparkling Mead, Chimay Blue, Old Simcoe American Barleywine, Old Cantankerous
Fermenting and Conditioning: Pseudo-Decoction Munich Dunkel, Left Hook Bitter
Recently Kicked Kegs: Fresh Hop Pale Ale, Citra Rye IPA
On Deck: Old Rasputin, Northstar IPA, Ur-bock Dunkel