n80
There is a lot of dubious "wisdom" in the audiophile world.
You’ll hear people claiming "break in" is required for literally everything to sound right...even an equipment rack, or a set of isolation feet for your component. It’s a sort of self-perpetuating mythology, because when people listen for differences they *hear* differences, even if there isn’t any in reality.
So you’ll see lots of claims that things like cables need "burn in." But what you will have a hard time finding is actual objective evidence for the claim (e.g. measurements showing audible-levels of difference between a new vs burned in cable).
The Burn-In mantra has of course lots of use for manufacturers to encourage you to keep their product as long as possible. "Not impressed by our product? Don’t just return it; Keep listening...it takes hundreds of hours until it sounds right!" That’s plenty of time to acclimate, listen carefully and over time come to believe you are hearing something new.
Others will likely chime in defending cable burn-in. Meanwhile, here’s a bit of reading for the skeptical side:
https://www.audioholics.com/audio-video-cables/audio-cable-break-in-science-or-psychological
Is burn in absolutely a myth? I don’t know. But most Electrical Engineers that I’ve seen discuss this over the years, who aren’t part of a company trying to sell boutique cables, tend to dismiss the idea.
You might consider that Belden, for instance, one of the world’s most experienced manufacturers of cable, and who supply to the professional market vs just honing marketing at audiophiles. You won’t find any "our cables need burn in time" from them. (And it would be to say the least awfully inconvenient for all the pro industries if burn in were the ’problem’ audiophiles think it is. Remembering that cables are used not only for high-stakes professional audio and must perform essentially right-out-of-the-box. But cables are involved in countless sensitive technologies, from medical imaging, to NASA. If cables really didn’t hit their specs for hundreds of hours and needed all this burn in time, that is a whole host of potential problems that...funny enough...you never really hear those industries worrying about. It's like capacitors/resistors burning in. If those didn't hit their values essentially right out of the box, that could be hugely problematic given the incredible number of highly sensitive instruments that use those passive parts. And you don't see industry leading manufacturers like Vishay warning for any of their product heading to sensitive industries like medical imaging etc "warning...100 hours BREAK IN TIME needed before these reach their proper specifications! ).