My daughter sleep by her own room after 3yr as I told her that her best friend also sleep on his own, plus I said only baby will sleep with mommy, so she wants to grow up and show to us that she is a big girl. It works very well. Once a while she will come to us, but I will tease her that she is a baby, she will go back to her own room next day. Now my husband miss her and want to sleep together if the weather is very cold here.
Yes, I agree that it is good to sleep with child before 3yr as they need more attention, but after that, it is time to move on.