My latest finished piece has 33 layers in it. https://paste.pics/Q1TMV I usually keep hair in one layer, but I've started doing multiple layers so it has more volume. A lot of the time things are separated by joints or the actual layers of an outfit. The details of the face and eyes are on separate layers as well.

So probably over 30 or around that area with finished pieces, and for sketches about 5 to 10 layers. If I'm just doodling it stays in the same range of sketches, or it's only on one layer.