The TangoGyro centrifugal clutch has no springs to be fatigued by heat-cold cycling.  Instead it has a hot-wire-cut central hub that allows the steel legs for each individual shoe to flex outward as PTO shaft speed increases beyond ~2000 RPM and the weight of the shoes overcomes the natural form of the steel hub, thus engaging the outer drum.  

TangoGyro Centrifugal Clutch