Advantages of Annuity Purchase
An annuity can be purchased at any time after age 50 (55 from 2010). With an annuity, your fund is used to buy an income from an insurance company which is then guaranteed for life. (Some providers offer fixed term annuities.)
When you buy an annuity, you are generally making a trade off by accepting a lower income for the security of knowing exactly how much money you will get for the period in question (usually the rest of your life). Once you have purchased a lifetime annuity, you cannot change your mind if your circumstances change.