"Off" vs. "Standby" and tube life

You can put the amp into standby, or you can mute the amp, or put it into standby or you can select a different input than the CD player before turning the CD player off. The point is that the CD player MAY emit a pulse when it is turned off which you would not want to amplify and feed to your speakers.

Most tube CD player outputs simply use the tube as a buffer. These small signal tubes would probably last LONGER if you don't turn the CD player off. Turning on a tube results in a quick inrush of current that rapidly heats the tube causing stress. This is what causes most of the damage to a tube. I would leave the CD player on all of the time. Also, when you turn the CD player off, the capacitors in the player discharge. It can take a lot of time for the caps to fully charge up and for the player to sound its best.

The safety issue is not limited to tubes. The tube itself won't start a fire, but the failure of the tube could casue other components to overheat and create a hazard. But, that is the case with solid state gear as well. Actual fires from component failure is not common, but I suppose there is some risk of leaving anything on all the time. Unfortunately, I do have to leave my refridgerator on all the time (but not, I suppose, the interior light).