The benefits of radioactive iodine therapy for hyperthyroidism?

I was diagnosed with Graves disease 9 months ago and we tried medication for 8 months, but it did not really work, just slightly alleviated my symptoms. I got RAI 2 months ago and I honestly feel great. I can exercise and do not feel crappy anymore. Is it normal? I read I will most likely develop hypothyroidism. When will this show? Will I keep feeling better from now on?