Heard it constantly my entire 40-something years in JWdom. It always sounded unnatural and cultish.
Heard it during meetings and in casual talk.
Heard in used in 2nd person (addressing audience): "Friends, please get to your seats; the meeting is about to start."
Heard it used in 3rd person (talking about other JWs): "The friends were so helpful when we had a death in the family."
Some brothers used the term many times in one part: "Friends, please turn to chapter 12, verse 13." "You friends did a fine job on your parts tonight." "Friends, you are to be commended for your support of the CO's visit."
I admit that there were some things that didn't feel right to me as a JW that I went along with and did anyway, but using the word "friend" as described above is one thing I never did - not a single time.