Well, god knows changing passwords can be a PITA, and I got messages that my password would expire. A search for it only turned up information on Active Directory, which is not really useful for me.
Anyways, you can do it here:
Start > Administrative Tasks > Local Users and Groups > Users > <user>
Then just check the “Password never expires” checkbox.
You won’t find anything for it under the user account management in the Control Panel.