We do know that we have heard from people all over the globe. This condition affects people of all nations and ethnic backgrounds. Many are not diagnosed at birth, some are misdiagnosed. The book said life expectancy is very short, but I heard about someone who was an active adult. No one can answer how long a particular individual has to live.
Life expectancy has so much to do with the type of OP and the severity of symptoms each person has.
I personally know of around ten people with an intermediate autosomal recessive form of osteopetrosis who have passed the age of thirty. Most have chronic infections that require significant accommodation. People with the Autosomal Dominant form have no lowered life expectancy. With a successful bone marrow transplant, even those with Autosomal Recessive Malignant Osteoptrosis could be expected to live a long life. Unfortunately, this is all too rare at this moment in time.