Kevin
I am no way suggesting these be pulled every 100 or annual that would be over the top. Pull it once now, fix it if they are bad then go fly a few thousand hours then take a look again.
If the heart strands have workhardened to the point that the cable will break when bent 90 degrees its probably time to change it anyway.
Cables are even cheaper if you find a shop that can manufacture them rather than buying genuine. We manufacture our own to sample and they sell for around $700 Australian dollars for the set of 6. (thats approx US$420) If any one local wants a set I can make from my samples here to save downtime.
twenty hours of labour sounds a little high cables only took us about 16 hours for the six. We took the oportunity to pull the flaps, grease the rollers, remove the bellcranks and grease the bearings, grease the rod ends and remove corrosion on the bellcranks and re etch prime. Total labour was approx 38 hours.
Wayne
1/My parts book shows the same cables all the way through 337 production without change.
2 & 3/There were no signs of corrosion in the cable or ferrule.
4/ No wear due to abrading, I believe it to be internal wear in the cable due to the angle.
5/ Slight visible signs in situ but very difficult to detect.
6/ Tensile stress perhaps. But good old fatigue definatly. At 7504 hours with an average flight time of 0.7 that would be roughly 22,000 cycles of the flap cable
Call me if you want 07 3275 3210 at work or 0419 182 206.

As I mentioned to a customer yeterday his 70 model plane with 7,300 hours at approx 150 knots has covered 1,400,000 miles. These planes are not getting any younger and need TLC!!

Reagrds
KS