Auditory memory of sounds we're exposed too frequently over a long period of time is good: e.g. a parent's voice.
Auditory memory of a sound experienced once over a fairly short period of time, e.g. an auditioning of a new audio component, is very poor.
Hence, impossible to judge with your ears how much burn-in of cables helps. If you listen to them once, you can't remember by the time they're fully cooked. If you listen to them over a period of time, to form a more durable impression, you're actually burning them in while you listen.
All you can really judge is whether, subjectively, the experience of listening to them after burn-in is as positive to you or more so, compared to your judgment when you first listened. This isn't the same thing.