How long do bumble bee snails...

I just realized I've had the same bumble bee snail now for 2 years. How long do they live? It was bought a week after I got my first tank. It was an established tank bought from another reefer. Anyways it's over two now. I've lost it a few times for awhile, then it just pops back in. :cool: I just thought that was kinda old for a snail