My computer is never shut down, however I reboot frequently being that I play some games that is not natively supported in Linux. So I often reboot to switch over to Windoze.
So yeah, reboot every now and then.
I'm also told that SATA drives have a much higher tolerance to being on all the time vs IDE drives. Something about the way the power is... on IDE drives it continuously fluxuates which causes the drive to spin faster/slower, where as with SATA it's constant, real steady... Kind of like highway driving vs city driving with vehicles in regards to gas mileage.
Not sure how true that is, but it's just something I've been taught in my few short months in school.