Driver's License Renewal in Tennessee?

I just got a letter from the state telling me it's time to renew my driver's license. My current one is set to expire on my 21st birthday which is at the beginning of September. If I renew it now, I will still have the "under 21" label on the license. Should I wait until the day of my 21st birthday to go to the DMV and renew it, or will it be too late then?