I never change my Anti-freeze. The entire fleet, for nearly 20 years. NO failures or problems. Cooling systems stay like new.
FYI I have a 600HP Mustang Cobra that until this week had the original antifreeze.  Not Rust, clean as new and spotless internals. (Since 2002) 
I just add a 8 oz. to a Pint of Prestone AS-180 Complete Care every year.  I can't find it in any Auto Part Store, only On-Line. 
I also use a wetting agent.
PS. As I has to remove the radiator, I will Put new Antifreeze in the Cobra.  The Used Antifreeze will go in the excavator/ Pick-up Etc. as needed.