I've had two experiences. One of them repeated by other A'goners.
Replacing caps in Focals caused really odd surround sound like effects for about a week until they just magically went away. The other has to do with Class D amps. I was using a pair of IcePower amps and turned them off for a weekend. Came back, they sounded horrible. Took about 4 days of leaving them on to return. At least 3 other A'goners have confirmed this phenomenon.