Blog Networks

About 6 weeks ago I signed up for a blog network service for three of my favorite sites. They're all doing OK but I'm not on page 1 for one I really want to push. It's a competitive keyword and my best position was 17 (335,000 exact searches!). When I signed up for the network that site slipped back to 24 before I even started, so I used that as my starting point (24).

I'm allowed 20 posts per day so I divide them up among the sites; 10 for the site above and the rest divided among the other two. My posts are about 150 words (minimum 100) and maybe that's the problem?

Anyway, the other two have been stable (on the first page) but the one I'm really working on slipped back to position 36 as of today.

I planned on using the service for 3 months then canceling if I didn't see an improvement. Also, very few of the posts show up as backlinks when I do a google search of my site ("www.mysite.com"), some do but not the hundreds I've put up. The domains o9f all of these blogs seem to be pr 2 or greater and when I paste a portion of the posted text into google, google does find the post. So the post has been indexed but it seems most backlinks aren't being counted.

Am I being too impatient, or maybe the posts are too short? Or is the problem with the blogs themselves? Anybody have similar experiences or suggestions to get these backlinks counted?