Living into the 70s and 80s has become a common expectation. Living into the 90s and maybe the 100s is realistic as well. The National Institute on Aging reported in 2009 that the fastest growing segment of our population is the over 85 crowd. As we get excited about that, let's keep in mind that for each decade after the age of 25 there is a 3-5% decline in muscle mass. Over the age of 60, the loss becomes more like .5% to 1.0% each year. A loss of strength can translate into poor posture, loss of balance, and falls. There are gains to be made at every age. We don't think about it at 30 or even 40 and 50. However, by the time the 60s roll around, the past either catches up with us or makes us proud.
Resource: "Exercise For Frail Elders" by Elizabeth Best-Martini and Kim A. Botenhagen-DiGenova