I received an hour ago the approval email.
This is my timeline, unfortunately perhaps not very useful to anyone anymore, due to my mistake on the passport photo size.

12/30: Applied for a renewal for a 5 year old, at the US Post office, not expedited.
1/5: Request received according to online tracker.
2/9: "Processing" email received.
3/2: Received letter dated February 11th and mailed February 22nd about the incorrect size of the passport picture.
3/3: Sent correctly sized picture via regular mail to the Houston Agency at an address in Sterling, VA.
3/18: "Approval" email received.