In the first three days, yes, you need to discard the remaining starter because it has no bubbles or activity. But, you can add it to other recipes to make sourdough pancakes, sourdough waffles, muffins, crepes, etc. I saved the remaining discards from day 4 to 7 in the refrigerator and used them to make bread on day 7. Just like making your first sourdough bread.