American Express has a newish policy of phased retirement, which allows "soon-to-retire" employees to act as mentors to younger ones and pass down valuable skill sets that newer workers lack. From Business Week:

"Rather than retiring and leaving the company at once, participants gradually give up their day-to-day responsibilities, while replacing some of their free time with activities like mentoring and teaching master classes to their successors. In addition, they get more time out of the office doing whatever they want—be it planning for life in retirement or doing charity work...It also helps them avoid some of the emotional and financial hurdles of sudden retirement."

The Business Week piece is part of an ongoing case study. There are more videos (like the one above) here.