You know. I keep hearing this. And I know that sheaves that have run wire (whether diesigned for it or not) will have the groove worn in them that will kill rope halyards.
BUT IT IS REALLY NO BIG DEAL OR EXPENSE TO SWAP THEM OUT.
For about $16 we got four Vesconite sheaves, Margaret went up the mast in the bosuns chair and replaced the old aluminium ones in a little under 15 minutes. Job done.
Having gone over to spectra halyards, I am never looking back. The next project is to go for Spectra 5mm lifelines instead of the cable. Much friendlier.