Cartridge break in

Agree with Rodman and Mosin. With regard to Pops' experience, I've experienced both. Some cartridges change wildly in the first 25-100 hours, including basic changes in character - particularly at the frequency extremes. Others barely change at all.

Some suggestions:

Make sure you're cleaning the stylus effectively (ie, Magic Eraser + brushing) after every side

Make sure your LPs are truly clean

Check with VPI to see if they recommend additional headshell weight for the Kleos (they can provide)

Try increasing VTF in .01-.03g increments, listen for some taming of high frequencies

Try lowering arm height by TINY amounts, listen for closer integration of HF harmonics with their lower frequency fundamental

Try changing the phono input impedance, which is adjustable on your Musical Surroundings.

5-6 weeks of play about 40 hours can make some difference. I couldn't wait and recorded an album onto my Nakamichi Dragon right after I got my new Benz S cartridge. A month later I rerecorded it over just because I read about cartridge break in and wanted my recording to be the best. Well I accidently failed to record over first 15 seconds and when I played tape back there was a noticeable difference in the bass from the first 15 seconds. It had tightened up. The song started with bass drums so I didn't have any high frequencies to compare. I hadn't changed the bias or record settings because there had been no other tapes recorded. The only other thing that might could matter is the warm up time on the Dragon. I don't know if it was the same on the 2 recordings. Some Audiogoners could repeat this chance experiment and post their results. The song was Helena Beat by Foster the People.

If your MC cartridge is used and you've just had it re-tipped would it require break-in again?

That would depend on whether the rebuilder replaced the
compliance(the material in which the cantilever is mounted),
or not.

Thanks for the feedback.
I'm pissed with myself because the Aries/Zephyr combo was "dialed in." I was really pleased with the sound: violins had a woody mellowness without a trace of harshness; piano reproduction inched closer to how a piano sounds.
But I wasn't satisfied; more is better; a $3K cartridge must be better than a $1K cartridge.
Oh la…
In fairness to the Kleos, it is better Hi-Fi. It seems clearer and more defined but the result, for me, is a better look into how the recordings were made and not into the enjoyment of music.
I fell like the traitorous Cypher in the Matrix. I don't care if my system is not accurate; I want to be fooled by it.