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.

There is no fast way to find and delete spams , the only way is to make users wait untill they post a new reply or thread , but it will be annoying for some people dont you think?

Sigh, we already have a system in place which stops people from only taking content. (daily maximum and more stuff)