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In terms of on-page optimisation, I don't think an SE sees your adsense ads when it spiders to page, so it won't have any effect on optimisation if you add them now. (I hope someone will correct me if I'm wrong on this.)
Your SEO may suggest removing/hiding the ads while submissions to human edited directories are in progress, if they make your site appear too commercial. It depends on how much truly original content you've got.
I'd go ahead and put the ads in place now, but do it in such a way that they are easily turned on and off (e.g. in an included file).