Standard & Poor’s has released new criteria that could make it easier for issuers to structure bonds backed by some 40-year mortgages. One of the hottest of the new products currently on the market, 40-year mortgages are being touted as an alternative to interest-only loans. The idea is that borrowers can get the affordability benefits of IO loans by spreading out their amortization period, while avoiding the problems associated with payment shock when the…