Cartridge break in

IMHO and with LOTS of experience about 40-50 hours.

I agree. Sometimes it takes even longer. I find that it helps to log how many hours you are putting on a new cart. Its easy to loose track.

Varies with the cartridge/compliance material. Don't be surprised if you have to readjust the VTA, along the way.

Thanks.
Just switched from a SoundSmith Zephyr to a Lyra Kleos.
The Kleos has more of audiophile everything: bass, imaging, impact…
But the high end is too edgy for my system and vocals have a papery quality. I'm hoping that this will tame after some hours of break in.
Otherwise back to the Zephyr.
Rest of the system: VPI Aries 3, VPI 3D 10" tonearm, Musical Surroundings Super Nova phono stage, ARC preamp, Bel Canto Ref500 mono amps, Joseph Audio Pulsar speakers.

It varies. Suspensions for different cartridges are made from different materials, some soft, some hard. Different materials don't all wear at the same rate, do they? And, yes, the VTA may change during the process.