The vets in my area use the 1 year mark also. They also encourage feeding several times a day. Young cats have so much energy and need to refuel more often.
I have 3 kittens that were bottle fed. One is 3 months old and he eats more often than the other two who are 8 months old. All of the kittens eat more than my older cats. I have the youngest on a kitten food and the older ones on an "all life stages" food. They get canned food 3 to 4 times a day and dry food for treats and left out when I'm out.
I would think if they are hungry and eating well, just keep feeding them like you are now. When they slow down and start eating less then you can lengthen the time before feeding. If you want to change dry food at some point, just do so slowly. Sounds like you are doing what's right for them if they are growing and healthy. They are lucky to have you.