AS a newcomer to Iodine study and use, I have also been researching this.
Since I'm using Magnascent and following (as well as I can) an Edgar Cayce protocol, my answer will be different from those who are using other forms.
As far as I can tell, in all the hundreds of readings about atomic iodine, Edgar Cayce always recommended a cycling routine, which varied by the individual's needs.
Examples: take 1 drop a day for 3 days, then stop for the rest of the week. Continue cycle indefinitely.
or take 1 drop the first day, 2 the second day, 3 the third day, 4 the fourth day, 5 the fifth day, stop for two days, then start over again from the beginning.
or take 1 drop morning and evening for 5 days, stop for 2 days. Continue indefinitely.
And this is only a small sample of the patterns he laid out for various individuals.
At first I was perplexed by this. After doing a lot of reading I came to this conclusion: Cayce's Iodine therapy is based on the idea that many athletes use in taking muscle building supplements. If you take it every day, your body shuts down its own natural process because the supplement is doing all the work for it. Many people who supplement with DHEA find they must cycle it or it quickly loses its effectiveness. A friend told me she had been supplementing with DHEA but it only worked for a short time for her. I told her about cycling and she started a one day on one day off protocol. She told me later that the DHEA is now working for her.
My husband and I are only on week 3 with Magnascent. We are experimenting with different protocols to see what works best. My intention is to use a combination of knowledge (learning as much as I can from other people's writings and experience) and my own intuition based on what my body is telling me.