The total number of days of life for a lice is about 30-35 days. Head lice start life as an egg that is laid by an adult louse on the bottom of a hair shaft. A female adult lice when fertile will lay about 5-7 eggs every day for about 14-17 days before she dies. Lice eggs are within 1 centimeter or about a quarter of an inch near a scalp and are very small. The adult lice secretes a glue like substance to the hair strand so the eggs can nest on the hair until they hatch. This is why the eggs are often called nits. If they end up hatching, the lice eggs (nits) hatch in about 5-7 days or so and become a nymph which is a baby louse. Very shortly thereafter they progress into an adult louse and they start the cycle all over again of breeding and laying eggs and sucking your blood from the human scalp.
Successfully attacking the lice eggs is a key to ending a head lice infestation but a huge challenge. A lice egg is the size of a grain of sand, does not move, is glued to the hair, does not cause itching, and has a protective shell that product cannot penetrate. If you miss one lice eggs, the head lice infestation can continue for days, weeks, months, and even years.