I don`t know how hot, "HOT" is but my garage ranges from 50 degrees in the winter to perhaps 85 degrees in the summer. I`ve got clays that have been in their longer than 5 years and are still just fine, including some Mothers. Used some of it a couple of weeks back just to use it up. It might have been a wee bit sticky but as I remember, it is right off the shelf. I also have some Griot`s and some Poorboy`s that have been there that long also, they worked perfectly. I believe that clay in general, assuming you can keep the air from it, has a great shelf life.