My laptop computer gets shut off when not in use but my desktop does stay on all the time and I never turn my led computer monitor off until I'm completely done using the computer for the day.
I work at home blogging and I like to get up frequently to take breaks in between writing new blog posts, updating current blog posts and responding to blog comments.
I also spend the day promoting my blog as well and can't sit at the computer longer than 30 minutes at a time unless really needed.
So the monitor stays on for easy access and I find that I actually wore out an led monitor faster shutting it off frequently and turning it back on because the power button which is little broke with too much use.
My monitors still last a long time even when they're left on all day but only shut off at night.