stupid tube question of the day

I dug into the records and found that Alfred Kayser of KR Tube Products sold me my nos Mullards and advised me to not run the amp more than 4 hours at a time. That was over 3 years ago. Absolutely no issues with the tubes in that time. Also, the tubes I bought have almost doubled in price since then...

I believe turning the tubed device off for a short listening break (such as the few hours referenced) will not contribute to the overall life of the tubes. I think/believe it is better for the integrity (physically) of the tubes to remain at a relatively steady state and temperature versus cooling off and heating back up.

Additionally, with a lot of tube equipment that does not incorporate a soft-start type of approach for the tubes, it is my belief and understandinging that the turn on process is more wearing and a greater risk to the tubes than leaving them on for a mere few hours.

In such a case it would be my advice to leave the equipment running for a good portion of the day versus turning it off and back on. But please note that I am not a tube expert but have over the years owned some very good NOS tubes that I paid a fair amount of money for.

Ckoffend, your comment is consistent with my thoughts too. However, I am not an electronics techie, so I have no real basis for formulating a view, ergo why I asked the question.

There are a number of A'gon members who are heavily involved in tube based electronics. To be courteous, I will not mention names or their A'gon handles, but perhaps if they catch this thread, they will chime in with some recommendations and guidelines that are based on their considerable knowledge and experience.

No matter what you do, tubes will eventually wear out and that is a fact of life. The most important thing is just be reasonable and enjoy the music. If you plan on listening to music on any given day, leave it on for that day. I believe too that cycling tube gear on and off several times during a day can be more harmful than good in regards to tube life. A case in point is that Audible Illusions believes this is true and design their tube preamps where the tubes are always lit even when the preamp is powered off. But now I'm just talking tube preamps only.

What about taking steps to cool the tubes down while they are in full operating mode? Such as running a small, quiet fan toward the tubes. Say one of those super silent computer fans, or A.T.M.fans (Active Thermal Management)? Could providing a cool breeze or flow of air directed toward the tubes be a solution? Extend tube life? Or would that not matter?
As we all know-Heat is not our friend. Most tube amps and alot of tube Pre's generate significant amounts of heat which can't be a good thing, right? If one could lower the ambient temperature in and around the proximity of the vacuume tubes, wouldn't it stand to reason that life span and efficiency would increase? What good is all that generated heat doing anyway? Please advise.