Jerryh : do you have a reference for [stating] "at death they lose membership of the "faithful and discreet slave" body"
I really based that on the belief of Jehovah's Witnesses that the "faithful and discreet slave" only exists as a composite group while the individual members are part of the anointed "domestics" (who are also fed spiritually by the slave).
So, if you are no longer a part of that composite group [of anointed brothers serving at world headquarters who are directly involved in preparing and dispensing spiritual food], ipso facto you lose membership of the "faithful and discreet slave" body.
But I had a look around in the literature and there are many places where it specifies that the "faithful and discreet slave" is made up of anointed Christians on earth. (Watchtower 02/01/75 p.77 para.4; 05/15/95 p.16 para.2; 03/15/02 p.14 para.4; 03/01/04 p.10 para.9; 11/01/07 p.30 para.12; 02/15/09 p.24 para.2; 06/15/09 p.22 para.11; 10/15/09 p.15 para.14; "Organized to do Jehovah's Will", 2019, pp.17-23 para.4).
As an example, the 1975 Watchtower referred to above says :
As a congregation, body or group, the anointed, spirit-begotten brothers of Jesus Christ, while on earth, are called his “faithful and discreet slave,” or servant.The only place I could find that suggested the "faithful and discreet slave" retained membership after death was a commentary on Revelation published in 1918 entitled The Finished Mystery. In commenting on Revelation 8:3 it says:
And another angel. - Not the "voice of the Lord," mentioned in the preceding chapter, but the corporate body - the Watch Tower Bible and Tract Society, which Pastor Russell formed to finish his work. This verse shows that, though Pastor Russell has passed beyond the veil, he is still managing every feature of the Harvest work.
However, that idea didn't retain currency and hasn't been held by Jehovah's Witnesses for at least ninety years.