For older forums, some topics have been there for years.
Can't do post count access only as some topics are member group specific.
Also, some members gained a lot of post count previously but quietens down after they hit the post count group. Increasing the threshold makes it difficult for new users to hit the target.
Can there be a mod granting topic permission to specific member group based on recent replies? (eg. users in group A will be able to access the topic if they replied within the last 30 days)
This is to encourage more active participation.