A 6% $1000 par-value bond maturing in eight years and having semiannual coupons is to be replaced by a 5.5% $1000 par bond, also with semiannual coupons. Both bonds are bought to yield 5% nominal interest convertible semiannually. In how many years should the new bond mature? (Both bonds have the same price as well as the same yield.) Answer to the nearest half-year.