The rule of thumb is to use your age as a percentage of your savings to allocate to fixed income based funds (cash and bond funds) and the rest in stock funds (e.g. if you are 35, you might put 35% in bonds, 65% in stocks).
By coincidence, the central bank on Monday approved a new rule designed to protect consumers from deceptive lending practices, including advertising practices that say interest rates are fixed when in fact they're not.