On or off or standby ?

If you can afford the electric, then yes. Tube gear may also need new tubes sooner.

If the gear has a standby setting then use that. They usually are designed to keep that part of the gear warm that takes a long time to warm up. The rest can be off to save power.

On a CD player the front display lights and transport power is usually turned off on standby. The digital DAC part stays on.

System Arcam Cd33 no standby
Amps Arcam A90 and P85 has standby.

There are many threads on this subject I would do a search and puruse thru them and make your own decision. But in general my opinion is if you have a stand-by mode them use that; if not turn it off.

Chuck