Sorry guys, I don't think we'll make a rule like this. I can think of a few examples where it'd have a negative effect.
If someone goes to a show and comes here to post their pictures, interviews the band and comes here to share it with us, etc., I don't want them to have to post 50 times before doing that.
It might even have a worse effect on the forum if someone really wants to start a thread, sees that there is a 50 post minimum and starts spamming just so they can make a thread..
However, if you see someone post a thread that's already been made, feel free to PM any of the mods/admins, and we can close/delete it and let them know how to search.