[Hallicrafters] When do you replace tubes?

[KB9GKC at aol.com]

Tube Life expectancy is about 10,000 hours.  The transistor life expectancy 
is 100,000 hours.

However, over the years I have replaced many weak tubes (weak on the tube 
checker) but I have found very few dead tubes.

73
Douglas
HT-37 
SX-101A
10 element log periodic