How can I prevent people from editing their content after a period of time has passed?

Say a person writes a blog post, a wiki document, an article or a forum post.

We can lock down a forum post after <x> number of days to prevent replies.

However, I want to be able to stop people from editing their content after <x> number of days.

What I am seeing is a prevalence of people creating content and posting it to the site, sometimes it's really good, and we even share it on social media, boost it among companies we know, use it in PR, and they're onboard with it.

We have a policy that says any content contributed, we're allowed to do that with, and we have procedures in place to have moderators or admins delete user content upon request.

What we're seeing though, is that people contribute content, and then sometime later, they edit it and wipe it out, the title's still there most of the time, but the content of the post itself is wiped out, leaving something like "soft 404" in its place.

People also do this with comments, leaving chains of conversations behind, while I'd want to also prevent people deleting comments after a time, it's mainly the ability to edit this content that I'd like to time gate.

What's the best way of doing so to prevent this?