While waiting for the last two KM155ID1's to arrive, I implemented a simple counter in order to further test the nixies and the drivers:

It would have been possible to use only two or even just one nixie driver IC if I had chosen a multiplexed driver design. But since multiplexing the tubes could potentially lead to problems with high-pitched noise from the PSU or the tubes themselves, and since the clock is to be placed right beside the bed, I have opted for simple non-multiplexed driver circuitry necessitating a driver IC for each tube.

I have not been able to find conclusive information on whether a multiplexed design vs. a non-multiplexed design has any impact on tube life.

One downside to using a non-multiplexed design is that it is not possible to dim or control the brightness of the tubes. This will have to be done with an optical filter.