Does that reflect everyone else's experience with signing? My relatives keep saying "Oh, he's so smart!" and as much as I'd like to believe that (LOL), I actually think his communication skills are due to the sign language.
Another benefit of signing that I didn't expect is how much it helps us understand him. A lot of his words sound so similar or indistinct that it can be hard to understand what he's saying just by listening, but he signs while he's saying them, which means we actually understand him! That's part of the reason I know he knows so many words, I guess. But still, I didn't even think about that when we first started, and it's really cool!