I've never actually tested that out. If it's content I want long term, I simply download it to my local storage before deleting from Whatbox.
What I've found works best for me when using public trackers for new content is to set up a max seeding ratio and whatever relevant *arrs. Doing it that way means that I've usually been able to download the content and stop seeding before the swarm is discovered/monitored by those sending the notices.