Campaign data is available in your Campaign Dashboard for 365 days after the last mailpiece was created. After one year the campaign will be archived.
This means that Smart Send Campaign data is available for one year after the campaign is sent and Triggered Drip Campaign data is available for one year after the last mailer was triggered in the campaign.
You can still access archived campaigns to see campaign level delivery and response metrics, such as how many mailers were delivered, returned to sender, pURLs opened, etc, but you’ll no longer be able to view or export the details of the recipients in each of the statuses.