Potty training - done

Is it this easy? Four weeks ago, I started using "Potty Trainin 1-2-3" principles to train him. We did underwear during the day and diaper at night. He had two accidents at daycare the first week, one the following week and that was it. The first two weeks he didn't know to ask when he needed to go but by the third week he knew to ask and knew how to hold for a short time. The whole week we were in Hawaii, he had no accident despite all the travel, plane rides, car rides etc.  I thought night time training would take longer but then he didn't have any wet diaper in the morning during the third week. So I just switched him to underwear at night. No accident at all. We didn't have any use for training pants.