At power up all of the power supply’s capacitors are likely discharged and will present as a near short circuit to the charging circuit unless there is some circuit resistance. A diode is rated for a certain number of these events. Intelligent power supply design can soften the power up current draw risk for follow on components.

At college the main computer had a massive 19V power supply. We never intentionally turned that thing OFF because after only a few power cycles the 800 pound power transformer would fail. None of the service techs wanted to take that service call.

Another aspect of power up/down is the temperature cycle. Each part in the box is rated for a certain number of cycles of xx degrees depth.

With respect to my home computer, it is a calculation. Over time do the costs associated with power cycle, disk spin up/down driven failures overtake the power use and air conditioning costs? On that computer I had a hard drive failure after a year or so, a power supply failure after about five years, and a cooling fan a year ago. I’m now on the third mouse. It’s an early i7 based machine that is still not a slacker, but I would not recommend doing any heavy video editing on it. Yes, it would start up faster with a SSD, but I don’t sit and watch it boot.

It’s had a good run, I’m plotting it’s replacement soon — there have been three blue screens in as many months. Hopefully, by the time I’m ready to pull the trigger we will have better resolution of the Meltdown and Spectre vulnerabilities.