BestChange, for example, implements a rule that only 2-3 posts made on threads beyond 5 pages are to be counted. This is because mega threads are usually full of spam and posts beyond the 5th page are more easily missed than those made in the first 2 pages. Also, posts that are already buried deep in mega threads are normally less interesting because they are most probably just repetition of earlier posts, and posters probably didn't even read everything before joining the discussion.
Personally, I feel that this is a horrible rule and creates a ton of spam as well. I have over 6000 posts and I don't think more than 5% of them is written in threads that have less than 5 pages.
These threads are usually the 'most worthless' on my list when evaluating who writes where and what.
Forcing someone to open a 'how was your day in crypto today' spamthread because a post in Premier league thread is considered as spam is, well, not the best move you can make as a campaign manager.
Similar view as well, discussions that happen on mega threads such as premier league is usually about the upcoming match, match that just got over or on some news, hence content is always fresh. You don't need to keep up with old conten here because it's already spoiled.