While this is something we have considered - several clients have asked us to increase the frequency with which they can display Full Screen Messages - we decided to stick with seven days. 

This is because we tested different settings and found seven days to be the optimum frequency to encourage visitors to book, but not get in their way. So no, we don’t have any current plans to make this a customizable option, but we may revisit it in future as we introduce a wider range of message types.