I usually give mine a week to 10 days, but I plant directly into my medium unless I have older seeds that have dried out some. Is there a specific reason that you "pre-sprout"? Every time you handle a popped seed, it is a chance to damage it or pass pathogens to it. And it the seed broke out of its hull but did not grow through the medium, there is the likelyhood that something not good happened on the way from the glass of water or paper towel or whatever to the medium, unless you know that you did something like over or under water.