Yesterday, I was doing my job with Adobe After Effects on my Lenovo Legion Y520
Then, I render it!
It takes 2 - 3 hours to finish
I'm so bored to wait
So reclining on my bed (My Laptop on table and pluged in charge)
A few minutes later, I fall asleep when my laptop is on and rendering a project of adobe after effects.
Is it harmful to my laptop?
Yes
Nope, as long as it was plugged in and on a hard flat surface, it was doing what it was built to do. Nothing wrong with that at all.
Your laptop does not care a Tuppenny F**ck whether you fall asleep or fall dead.
As long as it has proper ventilation then its ok (cuz u kno that bish gets hot AF) it won't hurt a computer to stay on all night. If the pc is not in use default windows power options will turn off your HDDs and may even sleep but you prolly turned off sleep while plugged in.
Based on your description, your sleeping while your computer is rendering a project is not harmful to the computer. A few years ago, I would render a 40 minute video project and that would take 8+ hours. Start the render, before going to sleep, wake in the morning, render is done. Worked great.
As long as it has proper ventilation and it's plugged in, the computer is fine.
It is not a good practice.