"Every month" can't be correct... maybe when they renew.
I thought it seemed too often, too, but didn't want to appear not to believe my 98-year-old friend. She was still very sharp mentally at that time, and said the law had been created as a way to get elderly drivers off the road without appearing to be cruel.
By the way, this friend's father, Judge Lawrence Becker, was the Solicitor of the Treasury during the administration of Woodrow Wilson (1915-1919). She and her sister, who was two years younger, both clearly remembered running in and out of the White House as children.