Mundorf silver in oil cap burn in?

I was wondering if users of Mundorf silver in oil caps can enlighten me please. I have just changed the coupling caps in my 2A3 amp to the mundorf caps and must say that the sound is initially a bit harsh. Is this to be expected in new caps and what's the experience in terms of the length of time for adequate "burn in"
Any comments from users of these caps is greatly appreciated