On the main creator page, where you have the watch templates, My Designs, and Published Designs there is a little symbol of a watch with an arrow pointing to it from the left side followed by a number. That number is the amount of syncs that watch has. There is no way of knowing how long they wore your face but you can see just how many times that face was sent to a watch to be worn.
Where it says Published Designs there is the same symbol followed by a number and that's the total amount of syncs you have had across all of your faces. You can sort your Published Designs by recently published or most popular so you can quickly see your best preforming faces.