Microsoft Knowledge Base Article 239539 contains the following summary:
Certificate Services in Windows Server 2003 and in Windows 2000 Server For Microsoft Windows Server 2003 or for Microsoft Windows 2000 Server, the validity period for the Root certification authority (CA) certificate in Certificate Services is configured during the Setup process for Certificate Services. The following certificates are valid for up to five years. However, these certificates are never valid longer than the Root CA certificate is valid.
|• Subordinate CA|
|• Internet Protocol Security|
|• Enrollment Agent|
|• Domain Controller|
All other certificates are valid for up to one year. However, they are never valid longer than the Root CA certificate is valid.