I would like to know if there are any commonly accepted best practices for general day by day PC usage. Some systems are running Windows 2000, some XP Professional and they are basically only running your standard office applications like MS Word, Excel, Outlook, Internet Explorer. . . from what I monitored the systems are hardly stressed performance wise but people tend to leave them running 24/7 (of course even over the weekend and on holidays) and never restart just because they are too lazy. I'm a bit worried that these habits might wear out the PCs faster and more than necessary.
Are my worries groundless and is it actually better to let normal desktop PCs run 24/7 or should PCs be shut down as often as possible? Maybe there are some completely different best practices?