I struggle with this for my personal computer. The TV-computer combo shuts off the monitor (triggers the tv to shut off when there is no input) after an hour. An hour after that it's suspended, works well.
My personal computer though, sometimes I shut off the monitor, most of the time I let it run for the day completely powered. I have yet to set any type of shutdown or standby because typically I use it more than I do my tv (work, gaming, videos, etc on the comp). I know there's some power conservation I need to consider for motivation, I have no security concern atm with my standard main account and everything private is layered so inaccessible.
tl;dr
what's everyone else's setup like for when they walk away from the computer?
PC is powered off when not in use because it's only for gaming and occasionally a build server.
Laptop locked if I'm going out of sight of it, hibernated if I'm going away for more than half an hour or so/need to put it in my bag
Occasionally left on with the screen off if I need it for something remotely but then I'll remotely shut it down when I've got what I need