Yes: It would be a mind-numbing task to do
I see two practicable options:
- We lock old threads when they pop up and split out the new post into its own thread, essentially doing what the user should have done in the first place.
- We lock each thread that goes inactive for X days/weeks/months. This would have to be automated, though- it was the thing that came to mind when I wrote about the mind-numbingness.