well you really don't have to change it out very often
i would change like when you get to 30,000 miles
even then i would take it somewhere and get it flushed out
anit freeze helps keep the car cool when running
there are lots of tunnels that run though the engine to keep it cool
and over heating and in the winter antifreeze helps from freezing "anit - freeze"
only reason to change anti freeze is when you get it flushed
cause over time it will start to build up and clog those tunnels
bad thing
hopes this help
any thing else you want to know