Good question...
Two ways to look at it (and I don't know which one is right)...
A sharp pencil is still a sharp pencil, if its locked up in a cupboard...
Or... that an engine will seize up if not maintained...
I must confess that I fired up my Cyrus speakers this morning, after a period of about 3 months of non-use, and they sounded really thin, and distant for about half an hour... with no bass weight to speak of, but they've filled out nicely now, after about two hours...
So, I guess that the answer to your question is, YES, but for not so long a period as the initial burn in...
Anyone else have anything to add?