While this is true, the length of time it takes for a filament to fail due to depletion of the chemical layer that emits electrons is usually many thousands of hours - more time than your guitar amp will ever be powered up, so that is not a very common failure mode. Mechanical failure due to the stresses of repeated cycling of power and the associated thermal stresses is more common.
Consider the following tidbits of interesting information:
"A heater's failure mode is typically a stress-related fracture of the tungsten wire or at a weld point and usually occurs after many thermal on/off cycles. One way to mitigate this of course is not to turn off the heaters at all (one of your options). Another is to employ a negative temperature coefficient (NTC) device such as a thermistor in the power supply servicing the heaters. to allow the heaters to reach operating temperature more gradually.
When the ENIAC computer was built in 1946 using over 17,000 vacuum tubes, the failure rate was initially several tubes a day. Of course they were already on all the time. They derated the voltage (and current) going to the heaters and reduced the failure rate to one tube every two days (longest time recorded without failure was five days).
Leaving tubes on all the time can accelerate failures which occur over long periods of time (thousands of hours of operation). Cathode depletion is the loss of emission after thousands of hours of normal use, as it is poisoned by atoms from other elements in the tube. However, according to page 34 of the 1960's era book
getting the most out of Vacuum Tubes, this is fairly rare since by the time the cathode has lost its emission, the tube is pretty much dead for other reasons."
In addition, the biggest enemy of filaments is over voltage - even 5% overvoltage can be detrimental.
Ignoring power consumption, you are better off just leaving your tube amplifier turned on for longer periods of time rather than turning it on and off frequently over the course of a day.
Consider power consumption part of the price you pay to be a blues/rock god guitarist.