We recommend that you purchase your wall in advance, because when you do, you automatically get up to 72-hours for free prior to the event for testing and to ensure that your Tweetwall is not empty when it starts.
If you wait until the day of the event to purchase it, you will not get the free 72-hour pre-event window. Only the posts that occur after you purchase the wall will appear on the wall, unless you manually import them using our import tool.