Tube Burn-in Process: Psvane

My question is not limited to the vagaries of tube burn-in but to the life cycle of amps, pre-amps, and cables even. I'm about 20 hours into the break-in period of a quad of Psvane CV-181-T's in my VAC Phi 300.1 It's expected that right out of the box, they will play closed-in, frigid, as it were. At about 10 hours they bloomed deliciously, but shortly after, receded again and at 30 hours still haven't regained their exuberance.

I've noticed the same close-open effect with cables and other electronics as well.

Any ideas as to why ?
My pair of Shuguang Black Treasure CV-181Z took close to 400 hours to burn-in. Grant Fidelity recommends 150-300 hours, so you have a way to go.

My Psvane 12AU7 and 12AX7 in my phono stage took around 50-60 hours to burn-in.
Expect the full burn in to be at least 100 hours. It is a true odyssey of good to bad to good during that time.
Ah yes, the Stressless Chair. Back in the day I had one for a decade or more but at replacement time I was told they were no longer being made. Maybe they're back ?
Will they burn in just with the amp powered on, or does a signal need to be passed through them ?