All my cavaliers have had them and they have never gone away.
Monty has a large one under his chin and another large one on the back of his neck. These are about 7mm across and the one under his chin does get crusty, so needs cleaning off or it itches. The one on his neck can become inflamed , if Joly gets at it while licking him, but it goes pale again and doesn't seem to bother him.
Izzy , for most of his life, had a pale feathery shaped one on the split of his upper lip.
Both Teddy and Joly have tiny round , pale flat ones at various points on their bodies. These are so small that you only notice them when kneading a patch of skin between your fingers.
Barbara, Monty, Joly and Teddy.