Well, i run my computers 24/7. It started as an experment to see if it was true that it shortened the life of the computer. Results? its both true and false. While some puters have failed in less than a year, others like my pentium 150 compaq is still running after 7 years now.
So, what is the real answer? Its really just what you prefer. Back when i was runing Win 95 i had to reboot every day to be able to run the computer without errors. Win 98 did slightly better and Win Me i finally could go almost a week between reboots. XP has only slightly improved on times between reboots over Win ME. I do have a Mepis Linux Pentium 500 puter that i havent rebooted in a year. What have i found out by running 24/7? You need a real good UPS if you live in a state where there are lots of power outages. The UPS can save the puter from multiple restarts if the power is flickering on and off. I also found that you need quality power supplies in your computers. I have had 7 PS'es fail that were cheaply built . The quality built PS'es have never failed, even when i did not have UPS's hooked up. You can get some mighty strange behaviour out of Windows when it has to scandisk and reboot all the time. One puter Failed to boot at all because of a multiple failure of power while Windows was scandisking.
What do i like about running 24/7? I like that i can get on the puter in 10 seconds anytime that i want to. Turn the monitor on, wiggle the mouse and off you go. NICE. I keep thinking about smart houses that you can run just with voice commands. This will take a computer capable of running 24/7 for 30 years or more, as i dont see any other method to have a smart house without a computer built-in to the house.