On the Google Business Help forums, Jade Wang from the Google My Business Maps team announced that if the business owners fail to login to their Google My Business account and do not revert the requests from Google they will unverify the accounts. So ensure that you login to your Google My Business account frequently enough in order to prevent your verified Google business listing removed.
In the announcement, Jade Wang said, “In some cases, we may contact Google My Business users via email to confirm that they are still actively managing a business page. If a user is unresponsive to our attempts to contact him or her and has not logged into Google My Business for a significant length of time, then we may unverify pages in the account. We're doing this in order to continue to provide users with the best experience when they’re looking for local businesses like yours. If you find that a page in your account has been incorrectly unverified, please contact support to get assistance restoring verification.
It's a good idea to keep an eye on the inbox associated with your Google My Business (Locations) account. It's also a good idea to regularly log into Google My Business (Locations) to confirm that your business information is current and accurate.”Google To Unverify Inactive Google My Business Accounts!,