Our customers have stored their mattresses for more than 6 months. If the seal doesn’t leak and the plastic doesn’t rip, it should stay deflated indefinitely. If there is leakage caused by either damage during transport or improper closing of zipper then it can expand after a few hours. This is the reason we recommend to use straps immediately after the compression. This way the mattress will be held in rolled form even if it expands for any reason.