When you set up your ColdReach profile you have the option to decide how long the search data will remain after a search in a campaign.  You can set under the Total Antiquity (Months), and choose 1, 2 or 3 months to retain your search results.

The longest you can keep your search results is 3 months. 
The system automatically defaults to 2 months.  After that time elapses, the search data will be deleted.

Once the system purges data it is gone forever, and you would have to re-run your search to obtain results again.

A good workaround would be to export your search data into a CSV file that you can save.