Can you do anything to make power tubes last longer ?

Be sure you know what you are doing in setting bias on the low side.  If the measurement is in mA, the lower number means running the tube more gently.  If the bias is in mV, a higher number means lower current and gentler treatment of the tubes.

Be sure the voltage at your outlet is not too high.  I’ve seen 125 volts and higher from some outlets.  A variac, or even better, a stepdown transformer, can lower the voltage to something like 115 volts or lower.  Running tubes at, or slightly lower than recommended greatly improves life of tubes.

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.

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.

Yes, the concern over skin oil has to do with light bulbs, not tubes.  The oil deposited on a high intensity, high temperature light bulb will carbonize from the heat.  That leaves a black spot on the bulb.  The light from the bulb is absorbed by the black spot instead of passing through and that makes the black spot MUCH hotter than the surrounding part of the bulb causing that spot to fail.

Another piece of advice is to grip tubes which have a base by the base and don't push and pull on the glass envelope.  The concern is accidentally separating the base from the glass envelope.  

Also, if you do a lot of tube rolling, be aware that tube sockets have a limited life in terms of how many insertions and removals before the connection becomes less reliable.  An old time technician told me it can be as little as 30 insertions and removals for a socket to fail (i.e., cannot be re-tightened reliably).  If you do a lot of trials, consider using socket savers while you are trying to find the right tubes.

What is "normal" is not necessarily ideal for tube electronics, particularly vintage gear that was built for lower voltages that were prevalent when they were made.  As I mentioned above, my local dealer who only sells tube amplification often has customers measure their outlet voltage and then orders the right transformer for them to use on the outlets supplying their amp and other tube gear.  He prefers to run the gear at much lower voltages than is common.  This is usually the cure for premature tube failure.  He also has his customers bias amps on the conservative side.  This is consistent with Atmasphere's recommendation.  

My normal voltage has been, for the longest time very steady at 117 volts at the outlet, but has recently crept up to 119-120.  My amp is cathode biased so I cannot do adjustment, but typically, cathode biasing means conservative levels.  If my voltage rises more than this, I too will consider a transformer.

It's been a while since I ran amps that required biasing, but my approach was to start at the low end of the builder's recommended range.  Then, in part because I'm lazy and because I want to be gentle on the tube.  I would just leave things be and not bother to check the bias.  As the tube ages, the current flow drops on its own so the bias point drops.  By not changing the bias to compensate for the drop, i am actually preserving the tube, albeit with a small loss in output power.