I have chronic clusters and have taken 300mg of emgality since FDA approval for clusters. Prior to that I took the migraine dose: 120 mg... but they do "load" you with 240, the first month (240) was great, then subsequent months after (120mg) it didn't work... when I bumped up to 300mg it made my chronic clusters VERY manageable... unfortunately today I have a Neuro appt to tell my neuro that the emgality isn't working, that I am having terrible reactions to sumatriptan SQ and can need up to 4 3mg pens a day, and that I'm hopeless. Oxygen doesn't work, prednisone taper isn't doing anything, verapamil never touched me :/
Emgality DID help initially, so that alone might be worth it for anyone suffering from non-stop, debilitating clusters and is trying to maintain a career and life.
Good luck!