550 throttle cable

Anybody else find that the they go through throttle cables (the cable that connects left and right throttle bodies)? I seem to be replacing mine every 2 years because they they don't operate smoothly anymore, the accelerator pedal gets heavier and heavier over time. I find when I remove the old throttle cable, it works perfectly when I straighten it out, but becomes stiff again when I bend it in a u shape. The new cable feels the same straight or bent into shape.