Switch It Off or Leave It On
Its a common question. Is it better to leave the computer running all the time or and power up only when you use your machine?
I guess the answer depends on usage.
If you use your computer daily, and for several hours each day. Leave it running all the time, just switch off the monitor.
If you use your computer a couple of times a week, just to check your email. Switch it off.
Constant power-up and power-down of your machine exposes the internal components to high and low temperatures cycles. These do not help prolong component life. This is particularly true for RAM, processors, and hard disk drives. Constant heating (expansion) and cooling (contraction) of delicate electronic parts, results in premature failure.
Electronic components last longer when they are run at a constant temperature. That requires good cooling and ventilation (or even heating if the temperature is zero or sub-zero).
Most modern computers consume low levels of electricity. They run low voltages (either 12volt or 5volt) internally, and modern Operating Systems have a power saving mode, when not in use.
The only time I had a computer part fail, has been at bootup (when the system starts) or when there's an electrical surge/spike. Never while the system was left running.