We had a Novell server here at work that was up for 2 years until a extended power outage downed it. The thing would move around 10GB+ of data a day, 7 days a week, 365 days a year.
Personally I had a W2K Server running over 120days (suck having to move to a new place) that also ran FTP, proxy, and Shoutcast. I think it was WAAAAY past 100GB when finally shutdown.