So your goal is to make as many posts as you can or read and participate in discussions?

Yes it is possible to have less than 5 minutes as time difference between two non spammy post but it's unlikely someone will do that as a regular posting habit.

And the rate is limited based on your activity if I am not wrong and you will have no restrictions whn you reach higher ranks and one method is to buy a copper membership that gives the same accessibility as a member rank.