Neon lights

[Shrek]

I have a large collection of surge protectors and the neon lights age and start flickering,
but the time it takes for this to develop seems very variable (sometimes a new switch
may be flickering from the start).

I know they add helium to the gas to help 'ignition', and I wonder if the helium is leaking
out of microscopic cracks in the glass.

Reason I suspect this may be the case is that
"Super-leaks" have been the bane of scientists working with liquid helium since the early days"

Strange but True: Superfluid Helium Can Climb Walls

Quantum rivers, waterfalls and fountains you can see with your naked eye

www.scientificamerican.com

So, I have been replacing the flickering examples in the hope I will be left with a good set.

 

[Wirko]

Helium helps ignition? Perhaps initially, while the gas is cold. But when it's already hot... doesn't seem likely to me.

Also: all gases glow, they just need to be rarified enough to make ignition voltage low enough. Argon is usable too but so are others - N2, CO2, CO, methane etc. Here are some examples you can buy (set of 9 tubes, if the link works as it should). You may know the blue glow in vacuum tubes when eventually some air gets in. I'm not aware of any advantage of noble gases over others, perhaps just nicer colours when used in neon signs.

 

[Shrek]

I'm also wondering how to make an LED run off mains voltage without the losses a resistor would imply; mind you, the neon lights in the switches I use run in series with a 47kΩ resistor and so waste some power.

The picture in your link makes me think neon is particularly bright

I also really like the matte finish of the replacement (Carling) switches I use.

 

[Wirko]

I'm also wondering how to make an LED run off mains voltage without the losses a resistor would imply; mind you, the neon lights in the switches I use run in series with a 47kΩ resistor and so waste some power.

If everything needs to be packed inside the switch - probably no way. You can try with high-efficiency LEDs that are bright enough at 1-2 mA. A LED can't stand large reverse voltages, so you need to connect a plain diode (or another LED) in reverse, in parallel with it.

If you can afford a physically larger circuit, there's the capacitive power supply, basically this, but simplified:

Capacitive power supply - Wikipedia

en.m.wikipedia.org

 

[Shrek]

That would work