For people having retinis pigmentosa, how many years do they have before they go blind?

It depends: There are many varying degrees of retinitis pigmentosa. Some have an early onset and lead to very restricted vision by a person's teenage years. Others have a more gradual loss of vision into later life.

It Depends: Retinitis pigmentosa is a group of inherited disorders that cause degeneration of the retina and vision loss. Depending on the type, some vision can be retained throughout life, in other cases, not. The most common symptoms are night blindness and gradual loss of peripheral vision. There is a new retinal implant which restores crude central vision( argus ii) for those who are blind from rp.