Good idea to replace clutch and brake fluids every tire change, for some that will be every 2 years, others every 4-5 years. Mine still looks pretty clear after 4 years of use but will be changing it next year when I get the new front tire installed.
The DOT would argue with this; they recommend every 2 years, no matter what, because of moisture uptake. I change the clutch fluid every year because of the higher temperatures that darken it faster, and I don't want the clutch to stop working in a long crawl.