Hi Tamara, I first learned about using lava rocks from Maurizio Leo's blog about adding steam to your home oven, and he figures his bag of lava rocks will last him for life, so I really don't think you need to worry about them deteriorating very quickly. I just store mine in the cast iron pan I use for steaming, and, like Maurizio, I'm still on my first hand full of lava rocks after at least a year of use. Barb

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