You're kind of overthinking it, and it's difficult for someone to speak in absolutes because of all the variables. Have you taken a read through the GrowFAQs? Have you ever grown anything else from seed?
For instance, do you have 'em in soil or peat pots? How much soil is in the container? What's the relative humidity? How moist is the soil to start out with? I let the plants tell me, so I've learned to do it by "feel", if that makes any sense.