So, after a year and a half of recurrent head lice/nits on DD and getting rid of them again, I am going to start 'nit sunday' to try and keep them at bay. The problem is she's nearly 13 - how old would you keep doing this conditioner treatment for every week? There's no way she'd be able to do it properly herself, but they just keep coming back. She never had them before last January and no one else in the house has had them.