TVs that never got turned off.

[wkand]

The old Kingdome in Seattle had a bunch of old Conrac B/W monitors in the aisles for viewing game highlights, etc. Many of them were in use from 1976 through the 'domes demise in 1999. Not 24 X 7 but heavy use nonetheless. The concession stands had Zenith color TV's, 1976 vintage, to view games while in line for a Kingbeer. They were in pretty sad shape (out of focus images, convergrence gone forever) when the dome closed, but they still worked. Likewise Sea-Tac airport had B/W monitors for flight info from 1973 through a major remodel in the main terminal in the early 2000's. Those WERE on 24 X 7. No idea how much service any of those sets received over their lifespans, but a pretty amazing service record.