Here's a very good article from the Wall Street Journal about the differences between married couples who are looking at retirement. Specifically, the article talks about differences in when people want to retire, noting that the the subject is frequently not discussed in any depth until the decision is right on top of one member of the family.
As always, communication is key--partners should be talking about their post-retirement expectations in terms of lifestyle, location, and activities.
The article raises some interesting questions for employers with aging workforces. Retirement planning, especially for high-value employees, is something that should not be a surprise for either the employee or the company. But it's virtually impossible for a company to initiate such a discussion without being viewed as engaging in age discrimination. So it might not be a bad idea for companies to bring in retirement planning speakers who can broach with the workforce the subject of coordinated retirement, without the employer looking like it's trying to encourage people to get out of the way.