Concerned Mother of 20yr old female with dandy walker who was diagnosed at birth?

My daughter has a very severe case of DW she has the intellect of about a five year old very poor coordination, balance and very short tempered, but my true concern is average life span, i can find nothing pertaining to this topic in any of my research, Is there any one out there with a adult child, friend or family memeber with dandy walker who is much more advanced in age than 20? if so please comment and help ease a worried mothers mind, also she had a vp shunt put in at 3 months and it has yet to be needed to be replaced and she is 20, this does not lessen my concerns either. help with a little piece of mind if possible?