I'm going to go out on a limb and say this isn't quite "mint" condition.
Spongy foam rubber isn't the most resilient thing. I've seen these can last a lot longer with better care though. This is in response to a recent post on the John K Stuff blog showing one that's only a little dirty, but still looks pretty fresh.
This one is just a pinch away from being dust at this point. So take care of your foam rubber, and it'll provide years of disembodied pulsing head puppet fun.