The forum is fighting against spammers, there are a lot shills here, if the forum didn't have cool down of every post, they can create a bot and start to shill their shitcoins in every sections.

Honestly I don't think 6 minutes is really long, except you're forcing yourself to post as fast as you can.

Back in the days when I was still a newbie, I never experienced a duplicate error message but my post was not there, I guess you're keep clicking to post when you're still in cool down.