I told Mark it is a good idea to carry spares,
I was not aware of that when i said what I did, nor did I single out anything you said until you very vehemently argued that my statements as to the facts were simply an optional opinion. If you're hell bent on carrying around spare tubes, by all means, do so, but don't try to equate your gut feelings as valid technical fact.
I stand by that statement.
Obviously; that doesn't make it any more factual; that just makes it your personal opinion.
You are the one who came out with both guns blazing by stating who ever told you that is "full of shit". I do take issue with that.
Get thicker skin. I didn't mean to insult you personally and if you can't recognize a little hyperbole, I suggest you try to envision most of my more "vitriolic" posts with tounge firmly in cheek and quit looking for personal insults where none exist. We disagree, obviously, but please, cut the victim routine. This is the big boy forum where we sometimes talk like big boys and don't act like teenage girls making everything unnecessarily dramatic. I'm sorry you took offense to the way I phrased my statement, and if it really bothers you that bad, my PM box is wide open.
I may not come from a technical background but I do come from a user background of over 39 years. 8 times out of 10 when I take a amp in for work it is the preamp tubes.
Your "tech" is either being dishonest or isn't actually fixng things and isn't aware of it. There are several circuit faults that changing a preamp tube will temporarily mask, bad coupling caps being the most common. A new tube with a slightly different plate impedance or tonal response can stop or mask decoupling oscillation, which can have symptons of anything ranging from 'weird' tone to ghost notes and feedback. Changing the tube can make that stuff stop, but it doesn't fix the problem, nor was the "old" tube at fault.
"No, my experience is that it is not neccessary. Anyone can have an opinion; I speak from a position of technical expertise" Still just your opinion.
Really? Then please supply me with the cathode currents, transconductance data and/or shorts/faults of your supposedly "bad" tubes. Let's see how my "opinion" matches up against the tubes' spec sheets.
Ahem -
If I may interrupt, can someone tell me how they determine in the field:
1) That a tube has failed, and;
2) If so, which tube?
It seems to me that unless both of these can be achieved without testing equipment, the issue of carrying tubes into the field is moot.
Yep. I asked the same question earlier: 'Why change them?'
Hey ppl stop fighting, we're not in TB anyway. 
Being the mod, and it's my call, let me explain why I feel this type of communication is important enough to take place here, even as contetious as it may seem:
these issues are not matters of opinion. There is verifiable technical data that directly addresses this subject matter, and to 'let it go' for the sake of "not fighting" does a disservice to people who come to this forum expecting facts. Since you mentioned TB, I'm going to use it as a prime counter-example. Unlike that forum, here, the science of electronics is not subject to a popularity contest or advertiser pressure, nor does it take a backseat to political correctness. I feel very strongly that it be presented accurately. There's no need for vitriol, but
vigorous healthy debate is a sign of good forum, not a bad one, that's why I've been so insistent on data or some quantifiable aspect that defines exactly how godofthunder's preamp tubes are not living as long as I state they should.
What kind of jobs do you all have that you can sit here in the middle of the day and argue nonsense? I want to apply! 
...lunchbreak, my friend. I do enjoy this forum.
