The lash has a growth cycle and unfortunately it is hard to determine which lash is ready to fall out naturally so it is unpredictable when applying the synthetic lashes. Each day we can lose 3-5 natural lashes, but often they fall out unnoticed unless they fall into your eye, but when eyelash extensions are applied we are more aware of when they shed as we know the extensions are there plus they are longer, darker and thicker. If you sleep on your stomach with your face squashed into the pillow or you favour sleeping on one side you may notice the lashes may not last as well as the other side.