If it is PINK then it is the Ultra Long Life not the older Red Long LIFE. This is my $.02 I think it is better to periodicly change out some of it as a refresh then to let it go bad and need flushing. The Pink stuff comes premixed 50/50. It usualy sells for $12-$14 a gallon. I would drain the radiator and the resovoir every 2-3 years and refill. This usualy gets about 50% of the coolant out changed out. THis means that you never get oxidation,corrison or deposit issues and you never have to worry about flushing out the system either. I usualy do the same thing with transmission but do it by milage usualy every 18,000-30,000 depending on how much fluid comes out!
My Camry Radiator and resovoir holds exactly 1 gallon of premix pink ultra long life coolant. It is too easy to just drain the radiator and resovoir. I always was the resovoir out just for good measure.