4 year old and his blanket

I have a sweet natured if not somewhat aloof 4 year old boy who is extremely attached to his infant blanket. At first I thought it was ok for him to keep it for comfort during a transition period when my girlfriend and I moved to a new home (we share 50/50 custody with his mother so he bounces back and fourth from our houses).That being said I want to have him start stepping away from the blanket as he is getting older and is starting to go to school or stay at his cousin’s house.Is it normal for a 4 year old to be so attached to something like a blanket and should we be concerned as his parents? via /r/Parenting http://bit.ly/2WKW4Zy