On 03/10/2012 01:25, Phil Allison wrote:
There are many applications where incandescent lamps are turned on and off
constantly and their life span is the same.


There were many installations using thermionic valves where very long
life was achieved by leaving them running continuously. The GPO had
discovered this and it influenced Bletchley Park with their early
computers, some did not believe they would get a reliable system but the
GPO engineers working there convinced them that it was possible.

There are frequent stories in the press of incandescent light bulbs that
have been running continuously for very long periods - tens of years.