I did try that some years ago for maybe a week or so. It does strengthen the skin barrier, which I think reduces the lesions a bit, but after a while it felt like my skin got an accumulation of dead skin cells, so I wanted to wash it again.
Not washing the face could be a natural form of skin hydratation. The top layer of the skin tickens/strengthens, sebum accumulates, which keeps the skin oily and reduces water loss of the skin. But that is also a perfect environment for demodex.
Nowadays, I only wash my face with cold water twice a day and use a moisterizer that I like.
About the reappearing of lesions after stopping with Soolantra for a few days, in my case this is also somewhat unclear. For me it felt like Soolantra reduced the lesions with about 95%, but I never reached 100% with it. But stopping with it also didn’t result in a clear comeback within weeks (It was only after using Sudocrem that I reached 100%.)