Is freon ever needed to add to ca units if your system is 6 years old and in the past couple of days the air coming out of the vents is not as cold as it used to be?

Six years old is not bad for an a/c system. Start by making sure your filter is clean. A dirty air filter can block air flow. Check and/or change the filter out every month. It is possible that there is a leak, in which case freon may have to be added to the system after the leak is repaired.