Concerns Regarding Postal Inspection Services Initiative for Move Update

So, one might ask, if these business mailers had such extraordinarily clean data, why were they visited by the Postal Inspectors in late 2008 and early 2009? With visits resulting in very large checks being written. How were these highly praised postal partners suddenly targeted for an audit 12 years into move update compliance? What action brought these valued, long time mailing customers into the crosshairs of the Office of the Inspector General?