I am really quite unsure why this suggestion is necessary at all - is it not just as simple for someone to set a timer when they are advertising to remind them to post again after 5 minutes? Almost every single cell phone and computer has a timer function. It would be more beneficial, imho, to add an auto kick for those that repeat the same message without following the rules. This would also allow the mods to watch for far more important issues which need to be addressed.
