The RDF system regulates the defrosts based on the actual time during which the display case has been open, reducing the number significantly. 
Let’s take the example of a display case set to defrost every 8 hours: if the gelato-maker keeps it open 6 hours in one go during the day and then another hour in the evening but then closes it, the display case will not defrost as it can still be open for another hour. Other settings can be used for defrosting or it can be started manually from the control panel but if you want to keep gelato in the display case overnight, with the display case closed, you can confidently leave it without any worries: it will be perfectly preserved.
The RDF system is an advantage not only for the quality of the gelato but also for energy savings, as defrosting obviously leads to high absorption by the display case.