Can you do anything to make power tubes last longer ?

It is almost always better to turn gear off when not listening and turn it back on when resuming a listening session.  Tubes are not light bulbs which are designed to come on instantly so they don’t suffer as much from thermal shock from being turned on.  Still, a lot of tube amps do employ some sort of soft start circuit that ramps up slowly and/or heats up the cathode first before the full plate voltage is applied (to avoid “cathode stripping”).  An amp with a tube rectifier can have the rectifier act as the soft start feature.

The other practice to avoid is turning off an amp and then turning it back on again after a few seconds; the discharge from the caps can be damaging under these conditions.  Wait a minute or two before turning the amp back on.

Amps that don’t need the owner to adjust bias (cathode biased) tend to run tubes more gently.  This setup does not allow the circuit to extract quite as much output from the tube, but the reward is often a longer life.

@xenolith pretty sure your balanced power supply doesn't regulate voltage.  Regenerators are the only power supplies I know that do.  

My amp has adjustable heater voltage.  I do have to adjust it for different driver tubes but I'm using a wide variety of type 10,10Y, 210, 801, and 801A tubes.  

Jerry

If the amp allows, does switching from Pentode to Triode make a difference?

Cryogenic treatment-surprised it hasn't been mentioned earlier.

Cryogenically Treated Tubes, the most cost-effective tweak for your audio system

 Of course, only for those who believe. 

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.