System to prevent leechers from making 100s of threads

Recently, leechers have been making LOADS and LOADS of threads to unlock content, after they do this they leave the website and don't come back.

What could be done to stop this; Anyone with under 100 posts (changeable) can only post 5 threads every 3 hours, this way they can't just spam threads. They actually have to reply to threads, and if they spam or anything they'll be banned.