nah theyre not vaccuum seeled. They're in a zip-lock style bag. I recall this question coming up in the forum before, I only remember I think that the consensus was a year. Honestly, I need to get some larger mice for Lars anyways. So not a huge deal. I bought large mice, thinking they'd be sufficient, and they aren't. He's currently getting a large mouse and a hopper from Var's outgrown stash. She'll be off weanlings soon too, so I have to order mice either way. But it always sucks to throw out mice if I myself or someone could use them, ya know.