A little more detail on my experience. Made 2 starters on Saturday AM 9/2 from a single vile. WPL500, best before Oct-6-12, lot number 1500IIL8298301. Seemed like not a lot of yeast in this vile. No activity by Sunday night, and getting ready to place an emergency order on Monday. Monday morning some activity, and positive action by Monday noon. Cold crashed on Wednesday night, and pitched on Sunday afternoon. Two 5 gallon buckets showing airlock activity after 4 hours. Both showing 1 inch of Krausen on Monday morning. Hope it works the same for you.