Thats really weird that a gastro would say Imuran works so slowly because of the tapering.
I started at Imuran on 75 mg (standard dose for weight I guess), and from what I can recall, It was about 2 months when I fell into remission. It wasnt a coincidence either, since I was flaring for years at that point. I had been sick since getting pregnant in 2000.
I did promethius test about 4 mths into Imuran, and was bumped up to 100 mg. Then a year later, bumped again to 150 mg. I always find it funny when I up my dose, since I havent had a bad day in years...yet my meds increase. I know its based on my blood tests...but I just associate taking more pills with being sicker.