8 ppm is a little high, it's not world's going to end high. You may notice some un-wanted algae growth. If that were to rise to 10 ppm, you could start seeing some color issues with various corals. Have you tested phosphate as well? What denitrification protocol do you have in place? My guess, is that if you're running a consistent 8 ppm of nitrate water changes are just acting as a band-aid anyhow. My nitrate doesn't change, it's consistently just enough of a tinge on a liquid test kit to show there is a trace of something, but not really dark enough to register as even 1 ppm. Many corals do best with a trace of nitrate in the water, but struggle once there is a measurable content for extended periods of time. My guess is you need to re-work your denitrification protocol.I am feeding heavy on purpos, I am two days late doing my weekly water change, and as you stated I am going to let it ride till next week. I tested today and my nitrates are the lowest they have been in months. I will test again 3 days just to see. FYI I am at a 8 ppm today
Thank you for your quick answer.