Personally I do Coolant Service every TWO years, instead of the "recommended" THREE years. I live in a horribly harsh environ heat, humidity and salt, thus, my desire to have a more "accelerated" schedule. I also change the brake fluid ANNUALLY.
Please use care when working with the coolant system. ONLY open the system with temps less than 90C, and do it SLOWLY.Wear a face shield, gloves and protective clothing.
I would strongly recommend the Vacuum Fill method. With the "Remote" expansion reservoirs, and their
"weenie" tube with go to the radiator, it takes a long time to fill with the normal "gravity" method..