Vanessa Fox of the Google Sitemaps team has posted at the blog that you should be expecting fresher query stats in your Google Webmaster Central area.

Specifically, every Monday, you should expect the data in the query stats page to be updated with fresh data.

Vanessa wrote;

Previously, we showed data that was averaged over a period of three weeks. Now, we show data that is averaged over a period of one week.

Discussion of this recent Google Sitemaps update at the bottom of this WebmasterWorld thread.