The appropriate thickness of polymer clay earrings can vary depending on the design and style you want to achieve. However, as a general reference, a thickness of at least 1-2 millimeters is recommended to ensure the strength and durability of the earrings. If the earrings are too thin, they may become brittle and break easily. On the other hand, if they are too thick, they may be heavy and uncomfortable to wear.
It is also important to consider the size and shape of the earrings. If you use contour cutters, you can play with the thicknesses. In the case of stamping cutters, you should consider a minimum of 3mm for detailed impressions, although you can play with more or less shallow designs. If you definitely need to create stamped beads with greater thicknesses, use an alternative system of stamping and cutting separately.
Remember that these recommendations are general and may vary according to your personal preferences and the style you want to achieve. Experiment with different thicknesses and find the right balance that works for you and your designs.