What is the best voltage for the IN-12 Nixie tube? Answered

I want to make a desk clock using four IN-12 Nixie tubes. Mostly, 170V or 180V applied to the Nixie tube. I want to know which part of the tube the applied voltage is affecting.

And I have found that current affects the lifetime of a Nixie tube, and I want to know if the voltage affects its lifetime.