In the book Dr D says to weigh every day, that way you will see the changes and rewards on a daily basis. If you have some of the tolerateds you will also then see wht works for you and what doesn't. If you see a stall or a gain you know that tolerated item isn't right for you.
I have been on the diet for 10 months, and apart from a few weeks after christmas, and this last week or so I didn't weigh every day because I am in my last stone and it is slowing down considerably.