Leave tube amps always on?


Mark, the owner of Linear Tube Audio, suggested I leave my tube amps on all the time 24/7 if im listenting every day, and to turn them off if not using for a period of time, a few days or for example we go away.  His reasoning was that it uses considerable more energy to turn on/off on a regular basis. 

Do others agree?  Kinda risky since these NOS Mullard tubes ain't cheap and will soon be gone forever.   
aj523
Per LTA's website " we estimate tube life for our amps to be in the 10,000-20,000 hour range."  Did they say what the tube life degradation from that level you'd experience if you turn it on and off as "normal" ? 
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Despite my question back to the aj523, I do agree with big-greg's & tvad'e No responses; I always switch my tube integrated amps, or tube preamp off when not in use. 
If you really want to know how to treat Berning designed gear you should talk to the man himself. Turn off when not in use I say.