Mr. Hunter posted a series of refferences about brake hoses not too long ago. One item was the expected design service life I believe.

Depending on the climate you live in will matter to some extent. It still is not wise to keep brake hoses in service over 20 years. You could look his items up.

Ours should fair better than southern cars I would think. Another rule of thumb that impressed me was if one fails change them all if of the same vintage. Really though it can be bad to have even one fail in service.

It is also reasonable that mercedes sources it's brake hoses from external sources. Most other manufactures do as well I imagine. Probably simular quality..