My WeatherCat install has been running 24 hours a day since September 2011 on my 27" iMac with the hybrid drive. Display sleeps, but the computer is awake.
WeatherCat, Plex Server, Security Spy, and Roon are all hosted from my computer and must be available constantly. About a dozen other applications are also always running (some in the background) such as Mail, Fantastical, 1Password, CCC, AdGuard, Dropbox, Alfred, iStats, and much more.
I restart every month or so if I think about it. Never had a problem. For that matter, I can't even recall the last time I cleaned the vents! Probably should do that...