[Amps] Shelf life of 3CPX800A7 tubes

[R.Measures]

**  Spare tubes last indefinitely unless there is a micro-leak in a seal. 
 If my amplifier used a tube that was still in production, I would not 
keep a spare, and I do not.  
--  Hazards to the 3cx800A7 are:
1.  Barium migration from the cathode's emissive-coating to the 
gold-plated grid caused by too-much  heater-V. (symptom:  P-out drops 
steadily during AØ)
2.  Cathode coating flakes off due to exceeding the anode-I rating. (can 
cause grid-cathode shorts)
3.  Gold evaporates from grid during intermittent VHF/UHF oscillations 
(causes internal leakage and/or anode-grid flashovers during operation - 
also causes reduced emission due to gold meltballs sticking to cathode).  

>Hello, I have a Ten Tec Titan 425 amp that takes the EXPENSIVE 3CX800A7 
>tubes. I am considering purchasing a set of brand new 3CPX800A7's for 
>spares while 
>I can afford It. Does sitting on the shelf in a controlled temperature 
>environment for several years degrade the quality of these tubes in any 
>way? ... ... ...