Shelf life depends on brand, packaging, and storage. Anbex IOSAT is FDA approved for 7 years.
Thanks - the ones I had were good for, I think, 3 years. Flushed them a year or two after they expired.
It wouldn’t hurt to have some on hand I suppose especially with a 7 year shelf life. I heard it doesn’t do much for adults because their thyroids aren’t really growing. Kids, on the other hand, benefit more; however, my understanding is that it prevents uptake of radioactive Iodine in the thyroid. It seems like that ought to benefit everyone so I’m not sure if I believe that it only benefits children.