There are ways to increase the lifetime of these tubes. Normally they're operated at lowish voltage and high current, which rapidly damages the outer phosphor layer. However,
they can be operated at higher voltage and lower current, leading to greater electron penetration and greater phosphor life.
Running at lower current would also likely extend cathode life. Note that most eye tubes have a space charge grid around the cathode, which both limits cathode current and
gives some interesting striations to the resulting glow. It would be handy if this grid were brought out to a separate terminal for greater control on emission. In most tubes,
it's simply connected to the cathode, giving essentially zero grid bias.
This is an interesting idea. Most of those one inch CRTs use an ordinary P1 phosphor (Mn-activated zinc silicate), which is a subtle variant on the willemite phosphor (Mn2+-activated zinc silicate)
used in eye tubes. I'm guessing the CRTs have longer life because of the aforementioned higher voltage and lower current. Some CRTs use an aluminized screen to increase brightness and reduce ion
damage, but I don't think any one inch units do. There are small CRTs with other phosphors, but they might not give the color you're looking for.
Similarly, there are some eye tubes (generally those with the phosphor deposited on the inside of the glass like 6HU6) which probably last longer, but they too are generally a different
(more blue) color.
Another possibility is a vacuum fluorescent display. These use a different cathode technology capable of extremely long life, as well as different phosphors (zinc oxides and sulfides) optimized for
long life at low voltage and modified for increased conductivity. However, they too are more blue than most eye tubes.
Once upon a time, there were very high brightness green fluorescent tubes used for copiers and underlights for escalators. These had a double layer, of white paint and
then green phosphor, along with a linear "window" where no phosphor was applied. These are capable of very long life, high brightness, and they're brilliant green. However,
they're large, power hungry, and hard to obtain these days. However, there are small colored phosphor CFLs that give nice pure light. One of these might serve.
There are also some Russian bulbs that work like the green NE-2 bulbs, but they're larger, about 1cm in diameter. Don't know about their lifetime.
- John