Password Cache

I have Windows 2000 boxes logging into an NT4 domain. My users are set up to log into the domain. They do not log into the local box. I have noticed though that if the network cable is unplugged from the pc, the user can still log into the domain. It looks like the box holds a password cache somewhere and authenticates against it if the domain is not available. I don’t have a problem with this. My question is, how long is this cache available? Will the system hold the password cache several days with the system powered down?