DSD7 came to our house for Christmas vacation with a headfull of lice. I was livid, because she'd been telling her mom that her head itched for days and while lice are quick and hard to see, they were so bad, that I saw several just by parting her hair with my fingers.
So, I spent Christmas vacation nit-picking. I had them all, and it was hard work. I explained to her that she needed to take her own pillow to sleepovers and to never, ever share brushes, hats, scarves, hair clips, etc.
Fast forward three months - two weeks before our trip to WDW, this past March - and DSD's mom calls to tell us that she has them again. It was her weekend to be with us, but DH told her mom that she needed to keep her and to get rid of them for good, or it could ruin our upcoming trip.
He figured that maybe if she had to sit there for backbreaking hours, like I had, that she'd be a little more careful about where DSD puts her head and what she puts on it.
Anyway, we found old nits two weeks later before our trip, and I had to worry the whole time we were there.
P.S. Come to find out, right before Christmas, her school had all of the kids take pictures in a santa hat. The SAME santa hat. I was furious! Schools should know better than that! We're pretty sure this is how she got them the first time, since the ten day timing from louse to nit made sense.