Google will very soon be checking the verified sites. This is to check that the verification HTML file or meta tag still exists. If it doesn't, the site loses the verified status and you will no longer have access to site statistics and diagnostics.
As you add a site to your account directly or adding a Sitemap for it, Google makes statistics and error information available to you. Google verifies the site owner before showing the statistics and other errors. The statistics involve Crawl errors, Indexing information, Information about violations of the webmaster guidelines etc.. While the range of might-be errors include Compression error, Empty Sitemap, Invalid attribute value, Invalid date, Invalid tag value and Invalid URL, etc.
Vanessa Fox, Google Engineer adds, "If you find that a site that previously verified no longer is, simply click the "Verify" link on the My Sites page and upload the file or meta tag again."