Yes your face does change after you turn 18 years old.
From the time you're born to the time you die your face does continue to change shape and features of your face change as well.
You notice the most changes in facial appearance from the day you're born until you turn 18 years old but even after you turn 18 your face continues to change.
For example if you look at a picture of yourself when you're a baby such as newborn to 1 year old you'll notice a lot of facial changes.
Then as you get older from 1 year old to 2 years old and 3 years old your face will look vastly different and then when you turn 5 to 6 to 7 to 8 and 9 and 10 years old and reach your teen years you'll notice even more changes in your face.
Your face gets bigger from birth to teen years and adult years and also changes shape.
You'll really notice a lot of facial changes from age 13 to 18 years old and after that the facial changes are not as noticeable for awhile.
But as you grow older and get from 20 to 30 years old your face will change more noticeably and then every 10 to 20 years after that you'll notice even more changes.