How long between the big sucking thing until a vampire is actually made?
This is uncertain. There is a period of time that the victim appears to be dead, but is not. See the vampire Pork & Beans in Never Kill a Boy on the First Date, who was in the mortuary; the vampire Stefan in Some Assembly Required, who was buried before he rose from the dead; and the vampire Ford from Lie to Me, who was also buried before he rose. However, in Welcome to the Hellmouth/The Harvest, Jesse is made into a vampire in a short amount of time and was never seen as dead. Buffy can somehow tell the difference between a dead person and one who will become a vamp. (She knew Ford would, but she also knew a person from Welcome to the Hellmouth was just dead.) Whether she knew Theresa from phases would vamp out is subject to debate. She could have been unprepared due to her shock about what Angel had done, or she could have honestly not known that Theresa was destined for the Vampire life.
