How long did you find the break in to be in speakers?
I used the CAST PIO Cu foils in my speaker (Tweeter 5.6uf) and DAC output coupling caps 1uf. In both instances they were improvements immediately after installation and just continued to improve. In recollection I’d say about 100 to 150 hours. Perhaps very subtle further improvement beyond those hours.
With Duelund CAST capacitors my assessment is you get what you paid for. Absolutely worth their cost given the better sound quality they yield. 10+ years now and still sounding beautifully natural and authentic.
Charles