If you are seeing the Hidden Lights off without your intervention, this is likely the Light Responsive setting kicking in.
When active, this setting will monitor ambient light. When enough light is detected, the helmet automatically defaults to a 'Daylight' mode which doesn't use the Hidden Lights and turns the Main Lights to flash. This mode is specifically designed for daytime visibility.
If you turn off the Light Responsive setting, your setting should remain unchanged regardless of light conditions.