My forum is almost a week old and Google has not crawled it yet. When I bought my IPB forum Google was crawling it the same day I installed it and hardly ever left. I just submitted a sitemap and installed a robot.txt. I sure hope it helps.
I knew google crawled the forum when it was IPB, I just checked it for XenForo links yesterday morning and there wern't any. It must have crawled the website during the day yesterday. It definitely makes me happy!
P.S. I can not wait to see how Google ranks the website!