Way to prevent new users from bumping old threads?

[XFFA.IR Bot]

We have a problem where a new user comes in and posts a reply to an eight-year-old thread instead of starting a new one, even though they had to acknowledge that they're bumping an ancient thread (thanks to an add-on).

Is there any way to prevent this?

All of my new users are in a special usergroup until they get 10 posts, so a usergroup-based solution is fine.

Thanks!