The popular consensus is that the less additives you add to a coral/invert tank, the better off you are. If it's not in natural sea water, you don't want it in the aquarium.
If you were going to use the prime, it would probably be added at the very end. The water running through the filter is pressurized. A tough time adding it before the RODI, plus, why would you want to put yet another element(s) in the water you are using expensive filters to clean?
FYI, I go through a carbon block about every 2 months and sediment filters about every 3 weeks. I change the sediment out when it's brown, and the carbon I go by the TDS meter.