The Notebook Review forums were hosted by TechTarget, who shut down them down on January 31, 2022. This static read-only archive was pulled by NBR forum users between January 20 and January 31, 2022, in an effort to make sure that the valuable technical information that had been posted on the forums is preserved. For current discussions, many NBR forum users moved over to NotebookTalk.net after the shutdown.
Some subscribe to the idea that because most components have a 'mean' time before failure that you will use up this 'time' quicker by leaving a computer (or any device) on when not in use.
Others believe that hardware that is left running will last longer as it avoids startup and powerdown cycles when can be damaging. In the case of things like solder joints around high heat components the temperature changes can break a solder joint and kill a component (look into thermal expansion). Hard drive bearings give more life when operating at their spec'd temperatures (expansion of metals, cold bearing = loose, hot bearing too tight).
You'll probably find the truth is somewhere in between, a computer that is hardly used may last 20 years... A computer that is always switched on like a large file server may exceed is mean time before failure and different components will expire at different times depending on their design and home users may go through more computers due to the higher amount of power up power down cycles.
If you leave it off for 20 years, it's going to last 20 years. The frequency that you turn it on and off probably isn't going to significantly affect how long your laptop will last.
on notebooks, the only major wearout parts are the chipfan, harddrive and LCD backlight. if you use power-saving modes, chances are it won't matter much. leaving the battery in acts like a UPS , keeping it from crashing if the power cuts out or sags . with notebooks, the power brick will sacrifice itself and burn out if there's an overvoltage like a surge or lightning strike.
on desktops it's a little more complicated b/c you have to consider ups/no ups, and also the micro-surges that occur when you turn the PC on is wear and tear on the PC components and can cause failures.
BUT if the battery is in place on a notebook you don't have these surges, the power circuits are extremely well regulated.
That being said, there's a counterpoint; older notebooks power circuit use liquid caps which leak with age, newer ones use solid caps, which theoretically should never fail.
Problems? See this thread at archive.org.
