The history will be kept until the Profile is deleted from the KACE Desktop Authority Manager Console. There are no settings to change or adjust the retention period.
Some additional details about the Profiles History option.
To access the Profile history do the following:
Navigate to Client Configuration | Profiles | User or Computer tab depending on which one needs to be reviewed
Select the Profile name and click History using the drop-down menu under the Actions box.

The Desktop Authority Manager keeps track of actions taken during the current session with the KACE Desktop Authority.
Example History window:

Click History to see the actions that have taken place. Click Undo to go back to a specific action or Redo to repeat and action that was previously Undone.
Operations may be undone by any user, regardless of who originally executed the action, as long as the user has the permission to perform the specific operation. If the user attempts to undo an action to which he does not have permission, the undo operation will stop at the point where the permission does not exist.
NOTE: History cannot undo the deletion of a profile. Please confirm the deletion of the profile before performing the action.