It depends on many factors, but moisture doesn't start being driven out of the oil until the oil temperature reaches about 180 degrees. This could take 5 minutes or 20 minutes, depending on conditions and how the car is driven. I know people who own GDI cars that drive 5 blocks to the train station twice a day and drive another vehicle on the weekends. Another factor, which you will see here, is people who drive by the MFI average mileage gauge to maximize fuel mileage and range. If you lightfoot the car around tank after tank, you're going to get buildup.
Symptoms are misfiring, stumbling, rough running, fuel mileage loss, and overall flat engine response.