I have several that are 3 years old. I suspect a long time if fed and kept in great conditions. I also have babies growing up and I am keeping these just to see how long they do live in my water conditions.
Yes, my babies were born in freshwater and have grown to the point some were sent out this past summer in snail packages. I have well water- really pure for today's standards, Ph is around 7.4 it does have alkaline in it but at the same time it is not extremely high - KH- It has no copper, no iron, no high phosphates, One of the reasons I have such great success with raising fish, most plants, and snails. When we build our aquatic facility it will be located here as I will not have to deal with city water and the associated chemicals.
For the same reason that Amano shrimp and countless other aquatic species live in freshwater but cannot breed in pure freshwater but require strong brackish to full saltwater...it has to do with the life cycle of the creature. This pattern (adults living in freshwater but larvae/juvies requiring brackish/saltwater) is a common pattern among freshwater aquarium inverts. Think of it as the life cycle of salmon only in reverse...salmon live their whole lives in saltwater, yet need to go upstream to freshwater in order to breed. For whatever reason, a lot of freshwater inverts simply do the opposite.