When I bought mine I put it in boat compartment and didn't use it and sometime later when I was to fish on another boat I decided I would use it. When I took it out of the compartment I saw that it had inflated and of course it was now completely deflated.

I rearmed it and started using it routinely then on one hot summer day I took it off and threw it in the bottom of the boat in the hot sun. You ask how fast does it inflate - well I can tell you it sounds like a gun shot and inflates that fast. Unexpected like that it'll scare the crappie out of you.

I rearmed it again and now wear it all the time winter or summer and now only store it in the tow vehicle to and from the lake.

I believe those tablets in the arming kit have expiration dates and should be replaced at times.