This is also why those power strip lights can sometimes flicker in the dark. They are sometimes over-driven for extra brightness; this does cut their lifespan, but they usually still last for many years regardless. However, towards the end of that shortened lifespan, the accumulated damage to the electrodes leads to flickering as it struggles to keep the neon excited. However, incoming photons can give just a little extra nudge, which sometimes is enough to keep the neon excited and glowing.