I would say reuse them, also check the service manual for Piston ring free end gap and Piston ring-to-groove clearance
That should give you the tolerance (standard and limit) and % indication of how much they are worn.
You need a good tool to measure this (feeler gauge / Thickness gauge)
If run upside down, might replace
if run without oil might replace
if run as circuit winning racer might replace (?, what do racers say?)
Pictures and walktrough might help others if you can, would be nice to see this job.
That should give you the tolerance (standard and limit) and % indication of how much they are worn.
You need a good tool to measure this (feeler gauge / Thickness gauge)
If run upside down, might replace
if run without oil might replace
if run as circuit winning racer might replace (?, what do racers say?)
Pictures and walktrough might help others if you can, would be nice to see this job.