There's a special script on attachmax that can delete any file on your webpage, by running a certain file on your webpage.

Via admin you can control the specifics.

Setting this allows you to: Start calculating the time until x(Days) has been reached.

So for instance, if you set (Days) to 10, then after 10 Days, this file will now be able to be deleted on Server.

This works in conjuction with the field:
(Min downloads per day to keep file saved)

Using these two factors combined you can set formula to delete unpopular Videos/Files.