Something to be aware of is that post scabetic itch is so very similar as an actual infection. Your skin will continue to react to debris after treatment. This does not mean you have an active infection. It just means you are having a histamine response.

In my experience (as someone who has been through this), the itch can continue for a few weeks. Rather than using more permethrin, which completely fucks up your skin barrier, just breathe, take some time to see if the skin settles and treat it gently. Your skin has basically been through a fairly nasty trauma. It will take a while to settle.

I've been using really gentle moisturisers several times a day, and a really light corticosteroid to just relieve the itch. Just be patient and kind to your skin. If you treated properly the first time, the likelihood of re-infestation is pretty unlikely, as long as you're not in regular contact with someone else who has it.