I shut down my laptop if I'm going away for a few days. Usually shut down and charge it, actually, so it's ready when I get back. And occasionally App Store demands I restart it. Other than that I just leave it in sleep mode.
Plus it tends to take ages to respond to the power button (rarely does actually, usually have to do that (threelettersthatIcan'tremember)-reset thing instead), so it's more practical to never shut it down, although once it responds to the power button it loads up pretty fast.