They last a long time but are not readily repaired. No voltage required. I just replace when they quit. Some one with more time and patience might try to fix or repair. But I don't see any advantage when there are replacements available. I hope this helps some.
One reason to try to fix them is to satisfy a sick need to make old parts like new again. Some of us are afflicted this way. BTW, has anyone successfully repaired one by using the bulb and its contents from a modern gauge?
