The spotlight has been on deferred income or longevity annuities of late, with new regulatory guidelines that allow them to be included in qualified default investments for workers age 55 and older. 

Traditionally, DIAs don't pay benefits right away but are designed to start paying out at an older age so that the annuity holder doesn't run out of income during retirement. Often they're set to begin payouts at age 80 or even beyond, as longer lifespans mean more time spent in retirement — and a greater need for cash to live on for a longer period of time. 

But that's not always the case. Sometimes people need that income earlier on, although not at the time of purchase of the annuity — and sometimes they find that their needs have changed.