Vanguard Wellesley Income Fund shows how a blended stock/bond portfolio can make investors money. : Vanguard Wellesley Income Fund celebrated its 50th birthday in July. A mutual fund being in business that long has become about as rare as couples reaching their 50th wedding anniversary, and so the fund’s longevity is noteworthy in its own right. But, by analyzing this mutual fund’s performance, we can draw important investment lessons for the future — especially about the wisdom of the so-called 60/40 portfolio of stocks and bonds. First, though, a walk down memory lane.