It is totally going to depend on your calcium needs. As it sounds you do not have much that impede on your calcium levels, however, your Ca levels should be tested to ensure your tank is balanced.
Media can last as a rather long time depending on how fast your tank depletes it. From your description it sounds like you do not have any large colonies of SPS or LPS that will deprive the water of Ca as the colonies grow.
Unless you have heavy calcium needs, you can often get away with using 2-part and magnesium additives to balance your system. For many systems this is the optimal approach as a Ca reactor if not properly dialed in and maintained can cause pH drops and spikes when the lights cycle from on to off and vice versa.
If it is going to be FOWL system, then I would go with 2 part and Mg additive, however, if you intend on keeping large colonies of SPS and LPS, then I would continue with the reactor and keep an eye on the media. It will slowly melt and turn to mud.
On my grow out tanks I made it a rule to remove the media from the chamber ever 3 months or less, depending on the Ca tests, rinse it, put it back in the chamber and replace what was used up. You can also add Dolomite to the chamber to help with Mg. However, the Dolomite should be the closest to where the CO2 is introduced into the chamber, top for the Lifereef system and should be be 1/3 of your chamber's volume.