since I only have one flask(2L) I make a starter and 24 hours later into the fridge it goes to help settle the yeast. then pour off the beer and add more wort(from the fridge, I dont want to shock it) place it on the stirplate and let it go. by the next 24 hours the yeast has visibly increased in volume, not including what krausens onto the counter. then I'm ready to pitch. unless you are making a very big beer 1L should be plenty for a 5G batch.