I use a similar method to Tackle Advisors video. I think it is fun to do but it is in no way necessary to do. With a polished drag surface the drag is noticeably smoother and has a more consistent startup.
https://www.youtube.com/watch?v=qfHrLUsl5Lo
The reel never stopped working. As for polishing the teeth of the gears it doesn't make a super noticeable difference in smoothness of higher end reels but on say on a Curado or Tatula it does make them feel slightly smoother. But with the bantam and antares I've done it to it just makes them have a slightly lighter start up on the retrieve.