This is a cool feature. This is immediately useful for documents that you only need or want to share with someone for a limited amount of time. I can also see use for this for instructors who want to use this for documents they share with a class of students, revoking access at the end of a term.
In testing I found that:
- any documents created inside a folder with an expiry set will inherit that setting.
- the expiry date must be set per person after the document or folder is shared with each person.
It appears that this addition became available in March.