I'm an engineer by trade, and by nature, and I can confirm that this was once an issue, and still is depending on the type of electronic being used. Specifically, when you have things with moving parts, such as traditional hard disk drives or optical disc drives, the power cycle absolutely is harder on them than simply leaving these sorts of things running. However, in the current age of NANDs and flash-based memory and drives, the 'to power off or not to power off' argument is mostly moot. There are pluses and minuses to both sides of the fence, and whether you choose to be on one side or the other, there's no clear advantage, beyond not constantly draining your li-ion cells. That's about the only constant you want to avoid, but even then, it's no guarantee that 2 different cells on opposite sides of the fence of use will actually end up ahead of the other. It just seems to be, on average, keeping your charge above 60% tends to result in a longer lasting battery life.