7591 PushPull Amp Adjustable Bias Voltage Setting

I own a custom-built 7591 Push-Pull amp based on the Pilot 240 circuit. It has an individual bias voltage pot and tap for each 7591. It was recommended by the seller to set "bias voltage" at -.55 volts. The amp has plenty of wattage to easily drive my modified Klipsch Heresys, so my thought was that I might try running the amp a bit "cooler" with less tube stress. I can find a lot of data on "bias current" adjustment for 7591 amps, recommended in the 27-35ma range, but don't understand how that translates to my amps "bias voltage" adjustment? Simply put, is for example -.65volts bias require less current and therefore running cooler? Also what would be the voltage range from running Hot to running Cool?
Without a schematic it might be tricky to offer correct advice.

Generally speaking though you are correct that you likely can run the bias a little cooler. The question is what would the reading look like? If you are reading a grid voltage, you would want it more negative.

To measure the cathode current, you would first have to know the value of the cathode resistor (if there is one) associated with the power tube or tubes. If you knew that you could then calculate the current if you were able to measure the voltage across that resistor.