After ordering aftermarket rear brake shoes for the 180mm drums of my 2014/2015 model, I was quite surprised to see how very little material the shoes actually have!
With normal use, I would expect the rear linings to last through round about the life of four sets of front brake pads or so.
The linings on the shoes are comparatively narrow at only 30mm width, the drums are small, and the "thickness" of the lining material is unusually thin.
My tiny and very much lighter-weight second car, a little old FIAT Seicento micro mini-car, with 39 hp has much bigger brake shoes with much more material! See https://en.wikipedia.org/wiki/Fiat_Seicento
There is an undocumented peek-hole for looking at the remaining thickness of the linings. It is on the brake plate, near to where the hand brake cable enters. The hole is normally closed up with a little oval rubber plug, and is on driver and passenger sides, one side mirrors the other. On the picture below, the plug is removed for looking onto the brake shoe. The last picture shows the plug in place.
Why is this undocumented? Probably because it was designed in the wrong place to be practical, on the opposite side would have been better and would have saved you from risking to dislocate your neck trying to see inside.
Picture below: The same hole with the the rubber plug in place (sorry for the dark picture!)