I leave my most frequently used computers (home PM G4, work PM G4, and iBook G4) on all the time. My iBook sleeps when I'm not using it, but I don't think I've actually shut it down in 2.5 years. My work G4 has been on almost continuously since January 2002. My home G4 I shut down if I'm going out of town for more than a couple days.

I don't know if it's right or wrong, but it's a heck of a lot more convenient.