I don't know if there's any 'official' data out there, but I assume 3 months would be typical as this is the guide most often given for how long to try a treatment before deciding if it's working for you or not. At least in my experience anyway - I've been told to give treatments 3-4 months by doctors, and I've come across this time frame on these boards a fair bit too.

Great, that is what I was thinking too. Its tough being so patient though!