when do I know if I have to replace the floaters ?

G.

Thickness (see workshop manual) and surface. a worn surface means "change me and plates!"

I mean the floaters that connect the outer brake disc with the center piece. Are they only changed when the disc needs to be changed ? Isn`t it that the floaters could have too much play ?

G.

There are "semi floaters" and "fully floaters". 907 have semi floaters and then rivets are quite tight, but in fully floaters rivets are so "loose", that friction part can move very easily sideways, when brake pads touch discs....

I would replace them with the disc replacement. Seems to me that they will wear out.

according to the info I have found the outer ring should move sideways but is not allowed to move front or back. If that is the case the floaters need replacement.
My discs are about new,

G.

When the rotors are disturbingly rattly soundwise, change.
When I had +0,8mm freeplay, sound was annoying although function was quite OK.
Changed floaters to 0,4mm freeplay, all OK, function also.
Freeplay rotation forward direction not a big problem, they do move a little.