OK, I am going to pull the trigger on a 24mg pen of Humatrope which I plan to use @ 2iu a day. I have a PDF from Lilly that says you should use all 72iu within 15 days. But I saw on Pfizer's website that Norditropin pens can be used for 5-6 weeks. Which one is correct? Can I use one Humatrope pen over a month?