I personally think it is not really necessary to change it every two years. I use a 50/50 mix of the orange Prestone 5 year stuff with distilled water in all of my liquid cooled bikes, and have for at least 18 years. However, I DO think it is mandatory that the brake fluid be flushed at least every two years. So, if you have the mid fairing off to do this procedure correctly, (proportioning valve access) why not go ahead and change the coolant also? Doesnt't take long and gives you a chance to check things out for leaks, etc.