We use a luminous phosphorescent paint on all our luminous watches. There is no specific length of time that the luminous paint will last for as it can vary, based on the following factors: The distance your watch is from an initial light source, the exposure time and the amount/thickness of paint on the dial/ hands/ batons. The phosphorescent paint may not glow and/ or may dissipate quickly if the exposure to light was not sufficient. The light emission will naturally become weaker in the dark as time passes.