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If you aren't seeing a loss of actual traffic from Google search results, then I would not be concerned. If you are, then track down what entry pages/keywords are suffering and diagnose that.
If you see less crawling with an established site this means more URLs are placed into the supplemental index automatically and less traffic is the result.
Since I'm here...another question regarding links.
Article writing: Do the search engines count as link juice published articles on the major article directories. How do they view published articles?
July - middle of September was consistent for my sites. As soon as the inconsistent crawling started I lost URLs due to supplementals. (analysis is based on more than 1M URLs)
The good news is as soons as they start crawling again all the URLs will be back in the index within a week.