This has been a problem for many of us for as long as I have been involved with RV’s. Distilling all of the threads I have read on binding control cables (from memory), the greatest enemy of these things is heat, and the RV-8 tends towards sticky mixture and throttle cables because they are easily (and naturally) routed too close to the exhaust. At least that seems to be the most likely cause since when folks replace their cables and take care to route them farther away from the exhaust (a small increase in distance works wonders), or shield them from the heat, cables go from lasting a couple hundred hours to a couple thousand.
If your cables are starting to bind, then yeah - I’d probably replace both throttle and mixture, since taking the quadrant apart is a real torture, and doing it once is better than doing it twice. Take care about your where the nw cables are relative to the exhaust pipes, and they should last much, much longer….
Paul