I was told that this was not encouraged on return to the airfield once it was within visual range as aircraft in the circuit just create screen clutter for ATC and can potentially cause TCAS alerts for other aircraft on approach?
The definitive answer about what controllers want has to come from a controller - but I know that quite often when I'm approaching an airfield, controllers will tell me "Frequency change approved, and it looks like there's several aircraft in the circuit there" or something similar.... so I'd guess that leaving your transponder on is definitely helping someone.
FFF
-----------------