Information
http://pubs.vmware.com/vsphere-51/topic/com.vmware.vsphere.security.doc/GUID-96210743-0C17-4AE9-89FC-76778EC9D06E.html
Solution
To implement the recommended configuration state, run the following PowerCLI
command-# Set the vCenter Password Expiration Value to 10
Get-AdvancedSetting -Entity $defaultVIServer -Name 'VirtualCenter.VimPasswordExpirationInDays' | Set-AdvancedSetting -Value 10
Impact-The password aging policy must not be shorter than the interval that is set to automatically
change the vpxuser password, otherwise vCenter might get locked out of an ESXi host.
Default Value-Password automatically changes every 30 days.