When you first mix a new starter, throw out the discard every day for at least the first week, if not two weeks. On the first days of building a new starter, the lactic acid and acid-loving microbes aren't present or thriving yet. You'll notice the smell of your starter may be odd or cheesy. Throw out the discard every feeding until the starter smells sour or boozy, after a week to two weeks of consistent feeding. After this point, you can use the discard to make crackers and the starter to make bread.