C. E. White wrote:

> The answer depends on on the particualr vehicle and your
> personal willingness to take a risk. Persoanlly, I no longer
> change hoses on a fixed schedule. If one looks bad I will
> replace it. Otherwise, I don't worry about it. Two of my
> current vehicles have "fail safe cooling."

I change my hoses every five years. I don't know if this is necessary,
but every water hose by then always looked and felt fine on the outside
but was cracking on the inside (hard crust formed), and I've read that
this cracking is caused by electricity flowing between the rubber and
the metal in the cooling system.