Modern operating systems include power management settings to conserve power when your laptop stays on overnight. If your laptop is working properly, leaving it on for extended periods is no worse than turning it off when not in use. The operating system automatically dims the display and puts the laptop to sleep after a certain interval, and waking the computer is faster than restarting it.
Connect Your Laptop to a Wall Outlet
By default, Windows puts your laptop to sleep after 15 minutes when running on battery power and 30 minutes when plugged in. If applications are running at this time, your display is turned off but your laptop stays awake. Depending on the amount of power left in your battery, Windows may cause your laptop to shut down before you return to it. Plugging in your laptop for the night uses slightly more energy, but ensures that your laptop stays powered on the sleeping state. However, leaving your laptop plugged in all the time reduces your battery's lifespan and the number of times you can recharge it. If battery life is a concern, only leave your laptop plugged in when necessary.
Heating and Cooling of Internal Components
Your laptop contains a fan to keep its processor cool when performing work. When sleeping, your laptop stops using its components and draws just enough power to keep your desktop's state in memory. If the processor is hot when you shut down or suspend your computer, it is no longer cooled by the fan but quickly returns to room temperature since it is not in use. Other components, such as the motherboard, RAM and electrical soldering, heat up and cool down through normal use, and shutting down your laptop doesn't affect their longevity.
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