you can use it throughout the entire flowering cycle for flowering enhancement, just make sure you're going easy on the phosphorus with your main nutrient set and don't use multiple flower boosters at the same time. the reason advanced nutrients says budblood is only for the first couple weeks or so is because they want you to use their other products, which you probably should have done considering bud blood is one of their most expensive flowering enhancers. And duh, that much phosphorus will jumpstart a plant no matter what nutes you're using. peace and good luck with your grow.