I agree, you should keep it. Esp if he still plays with it, humps it.. whatever
Peanut has a little stuffed bone he has had since he was a young pup, he loves that thing! I don't think I could ever throw it away, if it came down to it and there was a hole in it I would fix it. He LOVES that toy. I have to sneak around when I wash it bc if he sees me grab me and throw it in the wash he will pace around the house until I give it back to him!
I think its also something that we hold on to, that was his first toy...