Carver and Tube Life

I’ve been looking at Bob Carver’s statement tube amps, the Siver Seven 700’s.  These massive tube amps designed by Bob  have been around for years and the latest version of his 700’s can now accommodate KT120 output tubes and his best output transformer design.

EACH mono block uses 20 KT120’s! That’s 40 KT120’s total when it comes time to ‘re-tube.’  However, according to his description these KT120’s should easily last “50 Years”.  Is that truly possible???  Can the output tubes really last that long ?

It was a very sad, but also sweet to see Almarg's contributions to this thread. When we lost him, it was an immeasurable loss.

It was indeed.

Fortunately, his contributions and lessons live on. 
Carver makes a similar claim for his most recent amps. The output tubes apparently are operated at a cooler temperature than other traditional tube amps. The output tubes do get hot to the touch, but not enough to cause a burn. The other tubes are more typical types, such as 12AX7, 12 AT7, probably are hotter and may need replacement in a few years IMHO - never got around to ask Bob.
I cannot comment on the Silver Sevens. I do, however, own the Carver Crimson 275 amp, which carriers a long warranty on tubes.  I have made some amps and modify stuff for fun.  I can tell you that, while I'm not familiar with the circuits involved in that amp, in the 275 he uses a DC restorer circuit that is essentially lifted from television technology of yesteryear.  People were tired, presumably, of their TVs being "on the fritz" so they introduced the DC restorer to that product.  It may have been created way before for all that I know.  

The DC restorer regulates power so that big power tubes-a la KT 120s--can idle at <10 watts.  This results in efficiency and the tubes last for years.  
I have the deepest respect for Mr Carver but guaranteeing tubes for 50 years is a "politician's guarantee"; by the time the obligee calls upon the obligator, the obligator is long gone.