The interaction data tied to email performance activities within Luminate is only held in the system for one year. After the year is up, that data is no longer available for query or inclusion in engagement factor analysis or the Delivery Recipient report. The summary performance data will still be available, such as total email opens, click-throughs, recipients, etc, but you won't be able to see who these individuals were.
We remove this historical data from the system because maintaining this seldom-requested data would adversely affect system performance. We find that most clients are focused on their recent email performance data rather than looking back more than a year, so maintaining the very old data would hit our system performance without delivering a big benefit to clients. When it comes to data that's related to financial transactions, coaching emails, or actions taken, it will still be visible even after the year is up.