Is it advisable to power down CDP/Transport?

I am wondering if it is advisable to power down CDP's / transports when not in use. A very knowledgeable friend of mine mentioned that the laser life will be impacted if left on. I have never shut a digital piece down -- perhaps I should. The concern is only relative to the equipment prematurly wearing out. Any thoughts?
Leave it on.
Laser would not be on unless the drive were engaged (i.e. actively reading a disc- not in pause or stop). I think this is right.
Hopefully the pickup design turns the laser off when not actually playing, but who knows this for certain? I've always wondered about this especially since I had to have an aging pickup replaced, which wasn't cheap. This EAD machine never fully powers down; it goes into standby mode when the power button is turned off, which it should for better sonics vs. coming up stone cold. I guess the power switch only turns off the display on this one?