I usually grow a starter from slant, which requires very different timing.
A White Labs vial contains a ridiculous number of yeast cells compared to an original Wyeast smack pack. It was not uncommon to smack the pack on Friday morning, pitch it into a quart or liter of starter wort that evening, and brew the following day; therefore, 24 hours is more than enough time to start a vial of White Labs yeast. In fact, one can get away with pitching the vial the night before one intends to brew.