You need to create 2 Security Groups in your Server environment and assign the users to both groups. Name one "30dayschangers" and the other one "infinitepassword" for example.
The you must create two group policies and assign one policy to each group. In the group policy you can define the maximum password age for each group.
So far everything is hypothetical, I can't tell you what to click as I haven't setup such an environment myself yet. But it should work this way.
You will find advanced informations about group policies here.
http://www.microsoft.com/technet/prodte ... rngpw.mspx
best regards,
Andre Lorbach