Can you do anything to make power tubes last longer ?

I always keep a back up set of the full tube complement for each amp. I’m also checking bias every time I run the units --using a Fluke meter-- after the units have fully warmed up using a digital source for the first 45 minute to an hour. I do run them at exactly the recommended setting which is printed on the top plate, next to each tube socket). I often check them at the end of a listening session, too.

I used to never touch the tubes, using white cotton gloves to avoid any fingerprint oil, but abandoned that practice some years ago.

Lamm recommends replacing the driver tube--a 6N6P--every two years for optimal performance. I don’t use the amps constantly. I do know someone--perhaps the oldest Lamm dealer-- who runs his constantly. I get fairly long life from the amp tubes, which I buy directly from Lamm since the 6C33C not only requires burn in (which Lamm does, not sure what the failure rate is) but also has a peculiarity in the output stage*--each 6C33C has a different range in which they properly bias and Lamm matches, by serial number, a tube suitable to the particular amp for that purpose. I thus never tried to buy the tube on the open market. (The particulars for this are not disclosed by Lamm but in talking with another tube amp engineer, he seemed to understand this-- it might be interesting to get somebody else who uses the tube, like Ralph @atmasphere to explain the technical details). Two are in each mono amp- one as the output tube, the other used for voltage regulation. (* I gather that the tube used for the power supply doesn’t require the same degree of matching but since I get them all from the manufacturer of the amp, I am not sure).

One other thing I observed --the only tube I roll in the amps is the 12ax7 and have long preferred an old stock Tele ribbed plate (over the smooth plate). Many of the so-called NOS are, as you likely know, "pulls." I have been using truly never used old stock 12ax7s, a little more money but they seem to last much longer and the bias on the amps seems more stable.

Really, don’t overthink it. The lifespan will be determined primarily by the amp’s operational parameters (bias, voltage), and quality of the tube. Enjoy your tube amp. Vintage tubes tend to be very good, and long lived. But these days, most of what’s left there are used and will have unknown hours (many???) on them already. Russian power tubes have been very good for me, but they do fail occasionally, and yes "spectacular" failures (catastrophic short) can happen and take out a resistor. Replace those tubes every 2000 hours, at most.

Some of the amps with individual tube bias pots can be run colder or hotter, to get either (maybe) more tube life or more "class A" respectively.

Don’t throw a blanket over a tube amp, but don’t bother with useless tube coolers either. You’d only need a fan if you’re sticking it in a cabinet.

Don’t leave it on for a few hours just to save an on/off cycle. Just turn it on when you’re ready to listen. Unlike some SS amps, it should be at its best in 10 minutes. Any hifi amp you have today should be starting the tube heaters up well in advance of the high voltage, so it’s a safe start for the tubes. You would be hard pressed to find a tube amp anywhere that doesn’t have SOME mechanism for soft start.

On/off cycling the worst, in rush current at initial startups hard on tubes, rectifier tubes and/or soft start circuits, rectifier tubes may be sacrificial here.  Heat is the enemy of all components, my 845 SET amps, nearly 1000V at plates, cooling fans beneath amp to push heat out, 300B amps much less stressed by the heat. Quality tubes with good reputation for reliability.

Some amps just harder on tubes than others, some manufacturers really push with high plate and/or heater voltages. Do your research on amps, determine whether there is history of failures, this is number one with me. For some years I was having failures with a certain tube, replaced loosely spec'd resistor in heater circuit with much higher spec resistor, no further problems.

I agree that most tube amps sound good after a short warm up, it takes solid state gear more time to sound good so I can see why people keep solid state stuff on all the time.  There is no good reason to do that with tubes.

I also agree that many manufactures push tubes hard.  I think they do that in order to claim higher output.  It seems crazy, to me anyway, to prioritize high wattage ratings with tube gear.  

I run some very exotic, and very expensive tubes in my gear.  Fortunately, the tubes are run very gently and I have been using the same tubes for close to two decades and the tubes were already old and used before I got them (they tested good).  The only tubes that have ever failed on me were twin 300B tubes that are used as rectifier tubes in my phono stage.  They failed because a shelf collapsed and dropped a 15 lb turntable motor controller on top of the power supply to the phono stage.

@whart made a couple of points that I agree with. I check the bias frequently. I don’t have to use a fluke meter as my amp has meters for voltage and current for both the driver tubes and the output tubes. My amp is very stable but I have been rolling tubes a lot lately.

I also agree that there is no need to use white gloves. I’ll admit I’m an outdoor guy who doesn’t use lotion so my skin tends to be dry. but most tubes run cool enough that a little skin oil it isn’t a problem.

Thinking about this thread for the last day, I think the biggest factor in tube failure is running them at the wrong voltage or current. Most amps don’t have as much adjustability as mine. I’ve had amps with no adjustability (cathode bias) and they are designed to be easy on tubes--no action required.

I had a Decware ZMA and it had a great biasing system that I really enjoyed. it accommodates a lot of tubes and the bias current for each tube can be different. to calculate the bias current for a particular tube, look up the maximum plate dissipation on the tube data sheet (watts). Measure the B+ voltage of your amp. The best way is to use some insulated probes clipped to the correct pins (tube slightly elevated) running out to a volt meter. Make sure you don’t create a short to the chassis, turn your amp on, write down the voltage, turn your amp off and remove the probes. This number is important to know. Sometimes OEMs will provide it.

Divide your plate dissipation (watts) by B+ voltage (Volts) will give you amps. You’ll have a decimal. Multiply by 1000 to get milliamps. Now decide how hard you want to drive your tubes--usually a number between 60% and 80%- and multiply that times your current and that is where you set the bias. I have found recommended bias numbers well above what I calculated. I have also know guys who ran their bias purposely higher than recommended because they thought it sounded better. I think this is a myth, the "higher must be better" mentality.

If you have auto bias, you’re out of luck. I’ll never buy an amp with autobias.

Jerry