Oh Kay you are not being stupid at all, but I have to say he's still quite young. Of course they never live as long as we'd like them to (the rest of our lives would be great to me) but I have to ditto everyone else. Enjoy him while he's here with you and try not to think about the inevitable (sp?).
He's a wonderful dog and you take great care of him so I have no doubt that he will have many, many more great years with you