what will happen if my computer runs for 5 hours continuously every day?

What is your computer build first of all, can you let us know. Well, if you run a computer in a very hot place then it is possible that it will get overheated pretty quickly and then it will start to shut down either because of too much heat dissipation or something else. However, on the other hand, if you run the computer in a cool environment then you can run your computer as long as you want, noting that, intesive work like high end gaming, video editing, etc; on the computer is not done continuosly, though at some regular intervals.