At what age should a child stop calling their dad Dada n there blanket blankie

There's no rule for age. They are affectionate terms, so maybe never. My brother is 65 and we still call him "Bum-Bum" sometimes. (He was maybe three and wanted to be a bum so he could ride in boxcars all the time -- thus, he got that nickname,)

***ADDED*** When you refer to those things, say the word you want your child to use, "Father will be home soon, so let's wash up for dinner" and "Let me sew up that tear on your blanket." This is a tiny battle. As teacherjenn said, peer pressure may cause your child to stop using those terms. Meanwhile, choose your battles wisely!

It will change at some point, maybe when teased by a friend, or in the teenage years, or maybe never.

The parents should not use those terms, but allow the child to. They will change it, when they change. No need to stress out. (ok, if they are 32, living at home and still doing it, perhaps worry)