Your clients, Betty and Bob, are both 65. They are looking to you as their advisor to map out a financial plan that gives them enough funds to last both their lifetimes and/or one of their lifetimes.

Therefore, you need to know the likelihood of both or one living to age 75, 85, 95 or even 100. Knowing that probability acts as a guide to ensure they have the required sum of money set aside if they live to a healthy old age.