I probably go *at least* a year between water changes (partial water changes) on my approx. 130 gallon algal turf scrubber filtered system (which has been running well for 5 or 6 years now with a variety of LPS, SPS, and soft corals as well as macroalgae, etc. ). This system has gone 1.5 - 2 years or more with no water changes (and no obvious ill effects) on several occassions. I dose calcium hydroxide and C-balance, and I usually (but not always) have a bag of carbon in one of the overflow boxes to keep the water from yellowing (the carbon is usually changed no more than 2 or 3 times a year...usually the carbon gets forgotten until the water yellows and starts to bother me).
My multi-tank 400 gallon skimmerless, scrubberless system (deep sand beds and macroalgae harvest handle nutrient management) has been running for 2 years with just one 60 gallon water change a little less than a year ago (I removed the 60 gallons for another aquarist who was having problems with green water (!!!) to use for a 100% water change...the transfusion from my tank fixed his problems). SPS, LPS, and soft corals are doing well (though could be growing much better than they are at the moment if I was managing calcium levels better than I have been for the past year).
I'm not necessarily advocating such infequent water changes. I think there are probably good reasons why a bit more water changing than this could be valuable. Nonetheless, I have maintained very successful reef systems with hardly any water changing.
Bill