Agree leave it to the buyer. Realistically no rigger will certify 19 year old wire and there is no fool proof way of testing. (Have just been through this process). Equally the buyer's surveyor will certainly make it a "must do" and no insurer taking on a new boat will insure purchase without insisting on replacement wire. Fittings such as sheaves, rigging screws, toggles, pins, attachment plates for T balls can be physically inspected and often re-used.
So your choice is to replace the wire and hope you can recover the cost from the buyer or clearly state that the wire is original and set your price reflecting that. Worst situation is to say nothing to the potential buyer as the first thing he will do is try and knock the price down after his survey.