More homeowners are now choosing to lengthen their mortgage terms to reduce their monthly payments, but this can have crippling effects on their retirement. More than half a million retirees across the country have still not paid off their mortgages, according to new research. Over 500,000 older people may still be burdened with paying monthly mortgage payments of around £635 when they reach retirement age – which is currently 66, according to research from SunLife. Those on low incomes could see the majority of their monthly income going straight on housing costs which could affect their gene…