With my first computer I normally turned it off after use and never left it on and it died after about 2 years... On my Second computer i left it on 24/7 With occasionaly downtime for installation of various components but it has lasted me for over 4 years and now runs as a simple server at home again being on all the time My current computer has been running for over 100 days now since the last reboot and counting...
ITs on 24/7 now