Adele ring. In mathematics, the adele ring (also adelic ring or ring of adeles) is defined in class field theory, a branch of algebraic number theory. It allows one to elegantly describe the Artin reciprocity law. The adele ring is a self-dual topological ring, which is built on a global field.
Real softeners generally last 20+ years EVEN on ludicrously hard water while the service life on a pre-built softener seems to be under 5 years (if you're lucky) on really hard water and lasting longer than that is a rare exception.
I read somewhere once that a water heater typically lives for abotu 11 years. However my parents had the same one for over 21 years and had no trouble until the end. We use tankless water heaters which conceptually should last almost forever as long as the water is not hard or you descale them regularly.