Rhodopsin is extremely sensitive to light, so much so that white light actually bleaches the pigment from it and it takes about 30 minutes to regenerate fully. Much of it is actually replaced within the first five or ten minutes in the dark but while it
is depleted the rods do not function nearly as well in low light.
The useful thing to know is that Rhodopsin is relatively insensitive to the longer, red wavelengths of light so using a low powered red light will preserve your night vision as it will not reduce the retina’s Rhodopsin supply in the rods but it will allow the less sensitive cones to become active and give more detail.
Another related fact is that the cones are most sensitive to the green wavelengths of
light so in the absence of a red filter for your torch, a green lightstick is useful because the cones can function under very little green light, which because it is so weak, does little to deplete the Rhodopsin.
I have a couple of electro-luminescent light sticks which I use. I have found that they run well on rechargeable batteries and will even use the remaining charge from cells that are too low to run other devices.
Chemical lightsticks can be
used the same way but are much more wasteful being single use and requiring disposal after use.