New member here--first post. I don't have an answer to your question about how long to wait, but I wanted to say that prednisone therapy worked for me, but I took a really high dose for a few days and then tapered--the whole course lasted 3 weeks. Last year I did the same and it was very effective for a short time, but the headaches came back even before I was finished tapering off. This year, the prednisone more/less broke the cluster, for which I am extremely grateful. I'm not 100% free of pain, but I'm taking meds or hitting the O2 once, maybe twice a week instead of daily. I avoid triggers (alcohol, etc.), get weekly acupuncture treatments, and take lots of magnesium--that plus the prednisone have made the awful intense part of this cluster much shorter than usual, but like I said, last year it didn't work as well. Five months seems long for prednisone, but I'm not a doctor. Prednisone is great at doing what it does, but possible side effects abound. That said, we all know how terrible the pain is, so if your doctor thinks it's safe and you're tolerating it well, maybe it's worth trying. Let us know how it goes--good luck!