I had Jensen cap failures in Cary amps I ran some years ago, well known issue with those caps, Don't know if it was bad batch or inferior design or build quality.
I recently replaced four coupling caps in my 300B monoblocks with the Duelund CAST tinned copper, I'm with Charles in that they sound great right from the start, I do hear further opening up but I have a number of new components recently placed in service so multiple burn ins going on at present.
Just came upon this thread, haven't read entirety of it, but I run highly modified Khorns, using combo of Jupiter VT and Audyn True Copper Max in crossovers. Seems no one runs the True Copper Max, my second favorite cap after the Duelund CAST.