Lice eggs are so small you would never know if they hatched or not.
The only way to prevent them from hatching would be to remove them with a good metal nit comb, or your fingernails. Nits are laid by the mother and attached with a glue she formulates, to sit on the hair shaft in the perfect spot to incubate and hatch. The waterproof glue is so strong that they won’t simply fall off; they have to physically be removed!
Since nits will not fall off the hair shaft on their own – they need to be combed out or they will stay on the hair as it grows. So if you have very long hair, old nits (empty, already hatched eggs) or no longer viable nits (10% of nits will never hatch), could be left in hair for years. Since products like Center for Lice Control’s treat lice by killing off the lifecycle of the actual bugs, we really don’t have to worry about the nits and if there are hatching.
Whether the nits are hatching or not we need to remove them all together. Nits left in the hair from an old infestation can be confusing to a new head check like at the start of camp or from the school nurse. If they see nits present they must assume that person has an active case of lice. By removing the nits you are ensuring a clean head with no confusion.