I use this method even though I don't pump the clutch pedal so many times. The fluid is replaced every time it looks "wrong" and the time interval is sometimes only about 2 weeks of street driving.
I do/have done it to my '2 Z06, '3 Z06, '5 CTS-V, and '8 Z06. I even do it to my '11 370Z although it takes a lot longer time interval.
Should you do it to your '9? I would. If you're uncomfortable doing it, stop by and I can do it for you. I have a large-capacity syringe that can contain the old fluid in one stroke.