New: Pinched sound stage, aggressive highs, bloated bass, recessed mid-range and non-involving emotionally.
Broken in: Sound stage wide open with amazing 3-D imaging, soaring highs, tunefully correct bass lines, super present mid-range and great music like Bach’s "Air on a G string" just makes you want to cry.
This applies to most electronics, cables, fuses, new turntable belts (yes, turntable belts) in need of a break-in period, including cartridges. This, you can measure with your ears.
According to this logic and your description all new cartridges we are buyin’ sounds very bad and we have to live with this bad souding gear for a long time (just to burn-in those gear for up to 500hrs sometimes) as you said in another post. That means even if we play records for 2hrs per day we have to wait more than 8 month to finally get the sounds right. This is rediculous! Then people sells their cartridges for example (and lose money), often with just 200hrs on it, because they are not happy about the sound or always looking for something better.
IMO It’s better to buy used cartridges and used equimpent and enjoy them in full effect from the first listening session.
BTW thanks to the new manufacturers like Zu Audio who sells their speakers with factory burned-in drivers.