Change retention category on existing archives retroactive

If you have a retention category like "Business" and you make that the default for everyone, lets say it has a retention of three years. You then archive a bunch of items on 01/01/2012, those items would be eligible to expire on 01/01/2015

If you then change the retention category in the vault admin console to 6 years, then those items archived on 01/01/2012 will now be eligible for expiration on 01/01/2018.

Basically any changes you make to an existing retention category will effect ALL items that have been archived in that retention category.

As tony stated, when the expiration process runs, it then does its calculations on what items can be expired and what items will be left alone

So it first starts up and loads up the first retention category, such as Business and determines what its retention period is (3 years)...it then does a SQL Query to find all items archived with that retention category,  that are 3 years or older and that are not on legal hold.

It then deletes though items, and then moves on to the next retention category.
So again, if you change the existing retention to have a different period, the next time expiry runs, it will find items that are 6 years or older etc