Where can I find out how long cached credentials last in active directory

As far as I am aware, the cached credentials stored on any workstation will not expire. They will remain there indefinitely, no matter whether the station will be contacting the domain or not.

You CAN set the number of cached credentials a workstation will store, but unless you know you have changed this option, it should be set to the default and allow the user to store their cached credentials.

As always, remove the computer from the domain and cease all network connections, then just verify the user can log-in using cached credentials before they set off.

-tigermatt

Agree, there is no limit as to how long you can use cached domain credentials, even if the password has expired on the domain. I have a couple of clients, that have been using the same cached credentials for 15 months now, much to my frustration ;-)
There is a default limit of 10 saved credentials, but I believe that can be increased to a maximum of 50.

That is good info to know. This domain, and many of it's policies were created by a former administrator. I would like to verify this, where is the setting located in group policy?

You can't verify that setting because it because no setting exists.

You can create a new sub keys or edit in the following registry key to disable caching all together or set the maximum number of credentials saved.
HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon