Purview Retention Policies Best Practices

You need to understand the rules of retention as this is really important. If your retention policies are only configured to delete, then the shortest deletion will win. Read: Learn about retention policies & labels to retain or delete | Microsoft Learn 

Therefore, you must set the longest deletion as the default for all users; e.g., the organization-wide policy must be deleted after 7 years.

Then, create a second retention policy for deletion after 5 years and add a subset of users. Important

• If you use static scopes and add users' emails to a policy, then this policy can include up to 1,000 users. If you need more than this, you will need to create several policies. Read Limits for Microsoft 365 retention policies and retention label policies | Microsoft Learn
• Remember that with static scopes, if you delete the last user from this policy, then this policy will be reverted to all users. Therefore, you could be at risk of deleting content after 5 years. Read Configure Microsoft 365 retention settings to automatically retain or delete content | Microsoft Learn
• If you have E5 licenses, then create Adaptive Scopes, which are dynamic groups of users based on the user properties. For example, if department = ABC, or CountryorRegion = ABC, or use your own data with the custom properties. Then, you create the second retention policy (the shorter policy, delete after 5 years ) based on the Adaptive scope. This way you are never at risk of reverting back to all users.