In the film of Prince Caspian why Susan and Peter сказал(-а) that they will not come back to Narnia?

That's Because Aslan сказал(-а) them that they are too old for Narnia. However , Lucy and Edmund come back in Narnia once more.

if Ты read the Книги Ты will know but its because there 2 old E. and L. are coming back though

they сказал(-а) that they wont come back to Narnia because they are big enough,they have to live there own life.

i'm not sure...