My 2014 Optima EX has about 143,500 miles, I bought the car new. Although my AC is doing a decent job cooling with the HOT central Texas weather I was wondering is there a suggested time frame to exchange the 134A coolant I currently have in the car with new 134A coolant? I know with brake fluid over time moisture will find its way in needing it to be replace because its properties have changed. So, what your thought? Thanks!