Whats worse: cycles or hours?

If you use a surge suppressor, then turning it on and off should not matter. Typically components are destroyed from applying current fast when the devices are cool and they are thermally shocked. This is why most light bulbs burn out. Good electronics have surge suppressors built in to suppress current surges.

The number of hours on will definitely age the electronics more rapidly, so turning it off will extend life. However some parts will age naturally regardless and will fail over time, such as electrolytic (wet) capacitors from drying out. This is the number one failure of old electronics and may devices can (or should) be refurbished with new capacitors to extend their life. Ceramic parts age fine. Power resistors are another part that fails over time as well as parts such as transistors that dissipate alot of heat.

In general if a part gets hot, it will age faster. This includes parts that don't heat up but are in a hot chassis environment, but not all parts age at the same rate.

The TV will rot your brain, so use any excuse to turn it off.Your lap top computer should be off or stand by, if it is running on battery; Some people leave them on for days running on the wall wart = bad if it or the wall wart gets covered with a blanket, or even your dirty clothes. Most everything else; turn it off unless you expect to use it again in a few minutes. Neil

Turn it off....