Turn it off and see how is sounds from a cold start.
My CAL ICON MKII has been powered up 7/24 for 20 years (sans system changes/maintenance/power outages) and it's still carrying on and sounding as it should.
I never leave a CD in after play (gathered this info early on).
As Russ notes, this may be dependent on the specific deck.
My deck has gobs of separate power supplies (4-6+?) and I "guessed" that it was better to leave it powered up, plus it takes many hours for it to sound right from a cold start.