Almost all the videos of installing the gear change sensor I have seen show it being put down near the derailleur and I have read comments about cleaning being necessary. I live at the end of a mile of dirt road which is either very dusty or very muddy.

Recently I saw a 3yr old video by an Australian woman and she put it right next to the shifter. To me this seems to be a very good outcome for a little bit of extra fiddling around. What do others think, especially Johnny if he reads this?

Here is the link, and the relevant bit starts just before the 9min mark - https://www.youtube.com/watch?v=fqqoSZ-UsAw&t=10s .