i feel like i've heard something about 3 months being a fair trial period, as well. with my dd, we had several slip-ups, and it was about one month after being gf that i started to see changes. for her, it was two things - one, her ability to engage in imaginary play just exploded, and two, she started being affectionate (verbally and physically). can i prove these were related to gluten being pulled?- of course not. but she doesn't complain of her belly hurting all the time any more, so i'm game for a while longer.
good luck with your trial. i think it's a good thing to try for any kid. i'm gf now, too, and i think i feel better, as well.