I just put in Mundorf silver/oil caps in coupling position in my amp 2 days ago. They are on play/off/play burn-in cycle, but after a couple of days, they are already sounding pretty darn nice. I would say the worst of the burn-in goes away after couple of days.
The caps they "replaced" (not saying better or worse) were Mundorf silver/gold, which "replaced" V Cap Teflons, etc, etc.
More complete report to follow after full burn-in and testing.