When the children had nits it took about a month to clear them. The big fat juicy ones lay eggs and you have to comb out the entire life cycle.
First the big fat juicy ones
Then the medium ones
Then a couple of weeks of little ones
The teeny, tiny ones
When you get to the end of the teeny tiny ones there shoukd be no more because the little ones can't lay eggs.
Sit them in the bath, condition generously, section the hair and comb through each section from scalp to the ends.
The children found it absolutely fascinating and we used to line them up on the edge of the bath so they could have a good look.
I think the mega harvest was 37.
As soon as they were clear, ds had a no 2 cut.
DD was only about two and was thereafter trained in a thorough comb through every time she had a bath.
Neither dh nor I got them. DS got them due to ignorance and I didn't notice until I saw one or six. When that happens they have taken hold.
DC both were blonde so never saw any eggs.
DS never got them again. Because I was assiduous with dd I occasionally found a full grown one but thinknit had just hopped on --when she sat on the same table of one child whose parents were obviously not on top of it.