There is a big difference between a deliberate DA and a passive DF. Many serial adulteror witnesses just view a DF as a year or two time-out without having to do field service.
I know one elder who has been married three times and DFd twice - as a witness - and yup, they eventually made him an elder again.
There are other DFs who are not "passive" - like myself. I left the JWs during the Ray Franz episode and refused to go to judicial meetings or to write them any sort of letter. So- they DFd me about a year and a half later without any hearing.
And you can be very sure that I am certainly not going back.