Anchie, it took about 18 months from the time I was diagnosed with Graves disease to reach remission with antithyroid medication. My physician and I were both opposed to surgical removal of my thyroid or destroying it with radioactive iodine. I didn't want to trade one condition for another that would require lifelong, daily medication. It's my understanding that Graves disease is less common than Hashimoto's disease.
I also developed Thyroid Eye Disease, a separate autoimmune condition that affected the function and appearance of my eyes. Long story short, I had 10 sessions of low dose radiation to my eye muscles as well as surgery to repair my eyelids. One was drooping and one was retracted. Graves disease is remarkably frustrating for the person who has it and for the physician who is treating it. We just don't know exactly what causes Graves disease or any other autoimmune condition. On the other hand, it does appear that prolonged physical or mental stress, pregnancy and severe illness can trigger Graves disease.