Spreader sliding up

What’s the year of your 400 Nikolaj, Sparcraft or selden rig?

The inserts on the spreadertip, that prevent the wires from grinding into the spreader itself, can be replaced (as almost everything can be replace of course).

I routinely take my mast down every 2-3 years for a thorough check by a professional rigger that I trust completely.  He spotted material degradation on the mast around both sets of spreaders that needed reinforcement with 'mast doublers'; essentially plates that are rivetted onto the mast that function as new bases for the spreaders.  I could not tell that anything was wrong when the mast was up; rig tension was good, the mast straight and the spreaders were correctly aligned.  There were no observable symptoms when the boat was being sailed.  The cause is cyclic loading; even when alongside the mast is being subjected to constant forces as the boat moves thus stressing the rig.  I understand that without these doublers, sooner or later I'd have had 'spreader droop' as well as I do a fair amount of sailing in bouncy seas.