You can have auditing on when any user changes "Password Never Expires" option for any user.
Please follow below steps:
1. Make sure you have Change Auditor for Active Directory License.
2. Go to Searches - New and give name of search.
3. Go to What - Add and in newly opened window, under Event class, type "User Password Never Expires option Changed". You will see that event class - Click Add - Click OK.
4. Run this Search.