I say let them run for a while using moderate levels of music and let nature take its' course.
I remember hearing or reading years ago, that George Cardas had stated that anytime you move or re-position a cable, it will need some time to "settle in". I took that to mean a break in period, I would guess it would not be as long as when new, but let them play for a few hours and listen for any improvement.
I agree they will need some fresh breaking in. New connectors, new sheathing to split into bi-wire, mechanical stress to the cable, etc.
I have found even used Cardas may take a couple hundred hours to sound their best. The changes tend to be subtle rather than wholesale, including reduction in hardness or glare along with increases in clarity and refinement - in short, the same complaints most people have during the initial breaking in period for Cardas cables. We rarely think to ask the previous owner how long the cables have sat unused. As well, the speaker-amp interface in your system likely presents different characteristics to the cable from the previous owner's.