My Desktop machine runs 24/7.
It also acts as a server, so it does a lot of work overnight while I'm asleep. (Daily backups, other routine tasks like cleaning all the crap that accumulates during the day, etc.)
My Laptop runs when required. It takes a whole 15 seconds to boot up from scratch. Then it gets turned off. The laptop is a Desktop alternative, rather a main machine in its own right.
Oh. And the Raspberry Pi? It also runs 24/7 solely as my website server.