old 486 used for a file server and a 586 used for various other experimentation and print serving. Only time they have ever been down is when I needed to move them from place to place. Makes it about 3 years (give or take a month or two) between outages. I don't count power loss, as I don't have UPS. Even that only happens once a year or so, and the machines simply restart when the power comes back on. Pretty rugged old buggers.