Depends on the fertilizer. Usually, when it says it feeds up to so many months, they mean when mixed into the soil. You can mix all the ferts the plant can handle into the soil and then just water for 6-8 weeks, slowly easing into manual fertilizations at the end (or just transplanting). Or, you can mix nothing into the soil, even use a completely inert medium, and add all nutrients manually. All manual fertilizations should be alternated with plain water. Our veg mix in the 3-liter bottles lasts with no extra fertilizer except Maxicrop until flowering. The Maxicrop (1-0-4) supplies most of the vegging K and doesn't get mixed into the soil because it's very water soluble.