Will you have the software that automatically keeps you from listing/relisting after the third time?
It does probably need to be pointed out and made very clear that a relist is the same as a new listing and would count toward the 3 free ones. All using the relist function does is automate the process of marking an ad gone and creating a new ad. There's always a ton of confusion about that when it comes to the 5 ads per day limit, so I'm sure there will be the same around this.