Not familiar with that, I'm a ME. I was just glad my soldering was up to snuff. It was a challenge for this old woodworker.
What happens is that when one of the digits is lighted, material from the digit "sputters" off and coats the other digits and the inside of the glass envelope. This extra material is crappy, and adds a layer of resistance to the digits where it collects. Sometimes it can be removed by running a higher voltage through the affected digit for a while If you have a 160 to 200 V DC supply, you can sometimes cure it. (I thought I had a bad tube and fiddled with it, but the tube wasn't bad, I was just misidentifying the anode. Duh. So what I've written is based on the internet, I've never cured a tube myself.) Alternatively, some (most, I'm not sure) Nixie controllers "exercise" all of the digits frequently to extend their lives. There is interesting stuff on line about it. Having said all of that, the last tubes were made around 30 years ago, a lot of the ones you buy are used, not NOS, so I'd say that 12 years is a good run.
My physics work involves more EE than ME. I've designed the mechanics of cryogenic equipment, built some, but handed off most of the work to machinists who knew what they were doing. More an more, both the mechanical and electrical parts of the job involve putting together systems with off the shelf equipment. Not as much fun, but it works better that way!