it doesnt matter wether the PC is on for days or shutdown but it is better to off the PC after sometime,after all give it also some rest will ya !
I agree with you, but i shut down my system only once in 10 days...... If i have a problem or system gets slow..... or some installation or uninstallation required reboot. I just reboot.........
I haven't shutdown my office PC from last one n half year, though have rebooted it some times for updates.