I purge mine from time to time.

That's literally exactly why I'm using a new nsec. Leaked my own key in a screenshot. Thankfully only my Nostr key and not Bitcoin. I only keep paper copies of my bitcoin keys, though.

On my PC I have cron script that deletes files older than 30 days in my download directory. I think it's a great solution to purse digital minimalism and make myself aware of what I save.