[Boatanchors] Question about testing tubes

[Rick Poole]

Usually when I plug a tube into my TV-7 tube tester, let it warm up, 
and press the designated "Test" button, the meter rises to a certain 
level and there it stays.

Sometimes, the meter will rise to a value and then slowly fall off 
(whereas, for another example of the same type of tube, the reading 
remains steady).  Assuming the reading does not fall below the 
minimum specified in the tube test settings, is the tube OK to use, 
or does the falling off indicate the tube is on its last legs?

Rick WA1RKT