With new regulations, insured mortgages have a maximum 25 year amortization. Banks often choose to insure low ratio mortgages, and cover the cost themselves. Having insured mortgages allows banks to off load the risk and securitize these mortgages.
Consumers can choose to go with longer amortizations 30 or 35 years. These longer amortizations would equate to lower monthly payments. Banks are charging a premium from .1% to .25% on mortgage rates for extended amortizations. The increase in the rates cover the risk as these mortgages can no longer be insured.