for unbypassed cathode resistors. There are limits, however. Unless we are willing to use an extremely high power supply--say, 1 kV--we must accept a mere trickle current to accommodate a plate resistor that equaled 20Rk.
The danger of such a light idle current lies in the dragging down of the high frequency response due to the circuit's inability to charge the load (and stray) capacitance. Besides, the triode is least linear at the bottom of its conduction and the greatest amount of gain is not the same as the greatest symmetrical voltage swing.
(The hidden advantage to trickle currents is that the power supply design is greatly relived by wimpy idle currents, as the power transformer and DC filtering capacitor can be made smaller, i.e. cheaper; furthermore, it greatly extends tube life. But light current is not compatible with linearity and, over time, can lead to problems like the dreaded sleeping sickness. So, as many will agree, it is better to burn-out than rust away. )