Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

What size “nest egg” should my husband and I have, and by what age?
There are three numbers that matter in that calculation: 1) How much do you expect per month from in pension/social security/or other retirement programs? 2) At what age will each of you retire? 3) How long will each of you live? 4) What will your annual expenses be when you retire? Unfortunately #3 is the most important of the three and the hardest to know with any certainty.