JAM by Duelund

Yes these well damped, large and dense caps all take a good 300-500 hours to fully burn in. They will sound good after 100 or so and just continue to open up a get better. The larger the cap value the longer....closer to 500 hours. Many don’t wait long enough and change things far too early. They will sound good right away and up to 50 hours. At 50 hours or so things go worse unexpectedly. Yes, frustrating but true. However at 100 hours or so they start sounding good again and just keep getting better with time. This has been my experience and trust me when I say I have been through this cycle many, many times and know from experience.

I wish this were were not true as some think. However, it is the case and real on these caps.

I did burn in speed up for 4uF Duelund RS using Frybaby2 cable burner.
It helps. But in any case, it needs some number of hours of natural burn-in after a harsh Frybaby2 burn-in.

I received Jupiter capacitors and start running them in Frybaby2.
I think 3 days of a fast burn-in will be enough.

 I burned Jupiter Copper 3 days in Frybaby2.
I soldered capacitors into my phono-stage and listened. After that I connected Frybaby2 to phono-stage and run it about one hours. This extra hour didn’t do any difference.
The tonal balance after installing new capacitors was even. It looks like capacitors path about 90% of break-in.
Compared to Audio Note Copper capacitors that where before in phono-stage, Jupiter capacitors have more high frequency extension and bigger base. They have much more resolution in all frequencies spectrum included lower midrange. All violins, saxophones, trumpets have more body and midrange tones. Soundstage became more 3d and further.
Arensky trio with Heifetz- Piatigorsky sound more energetic and emotional. Most of jazz music sound more real. But on rock music Jupiter capacitors show more records flaws too.
I can compare Jupiter Coper to Duelund Custom Cu capacitors directly. But I changed Audio Note to Duelund Custom Cu in my integrated amplifier, so I can compare Jupiter Copper to Duelund Custom Cu capacitors indirectly. This comparison is based on my memory and not too accurate.
Duelund Custom Cu capacitors have bigger, deeper and slower base. Jupiter Copper capacitors sound faster and very energetic. Duelund Custom Cu capacitors have lusher, richer low midrange on vocals. Duelund Custom Cu maybe a little better in term of tone.

They do need more time to break in with music.  500 hours with music. Pretty sure your cooker time fell short of that. These do take all of 500 hours to sound their best. Not sure what the cooker equivalent of 500 hours is? Not sure if it even gives the same result?