While a complete denitrification cycle has definate benifits, high nitrates alone should not be the only reason to do a water change.
Frequent water changes do cost money (no one said the hobby was cheap
) are generally considred a pain and mine usually get messy ! There are however many benifits IMHO
You can replace with new saltwater many trace elements perhaps the latest snake oil doesn't have or the average hobbiest is unable to test for. Often before a water change I like to stir up any dead spots or clean the glass, blow off detritis from rocks and coral. Then use the water change to take a lot of that out of the tank. It (the bucket of water I remove)gives me a place to rinse sponges and pads. While most consider a water change a chore I enjoy the quiet time and spending time fiddling with the tank is as relaxing as at times it is aggravating.
Before I get off my soapbox I will add that anyone can complete the nitrogen cycle without a special filter. I have undectectable levels without a deep sand bed or chemical filtration. I use a berlin filter with skimmer and plenty of rock with two floss pads to catch the heavy stuff and break up the microbubbles from the skimmer. An inch or less of sand in the tank just for looks (and to help with the frags)
I have a CoralLife de-nitrator. It takes a couple of weeks to set up. I never got to use it because by the time it had built up a colony of de-nitrifying bacteria so had my reef. It was just another excess piece of equipment that required plumbing and maintenance that I did not need. So I took it off and never looked back. That was over 10 years ago and so far so good.
If a de-nitrator had other benifits for me, like removing heavy metals, aiding in gas exchange, providing a safe haven for "bugs", stabilizing the pH etc then perhaps it would rank up there with some of my other equipment (refugium). It doesn't so I don't use them. Just my opinion. Do yourself a favor and DO the water changes, high nitrates or not.
No offense meant no harm intended
SiF