This article originally appeared on LinkedIn.

The last time I quit a job, Gerald Ford was president.

I quit that job to go to business school, and then I joined Bain & Company and stayed put for more than 30 years. Why quit? Bain has been a great place to work and consulting gave me the opportunity to help companies around the world in just about every industry you can imagine, without ever changing the company name on my paycheck.

I’m also part of a generation that tended to stay in one place, but that’s harder to do in an era still smarting from two major recessions. Now, average employee tenure in the US is less than five years, according to the Bureau of Labor Statistics, and neither employers nor employees expect their relationships to last forever. Although it’s often hard for executives to see young, talented people leave their company, people often have to change jobs, employers or careers to broaden their skills and explore new challenges.

While these shifts can be rewarding to people, more companies are realizing that they also have a lot to gain when employees come and go. In fact, some smart companies, including Procter & Gamble and IBM, learned long ago that fostering positive relationships with outgoing employees—treating them as esteemed alumni rather than traitors—can help the bottom line. Here’s why:

It creates great word-of-mouth about your brand. If you’re cold to a person on his or her way out, you risk creating an enemy of your brand. In Net Promoter® patois, we call these people “detractors.” Detractors go out into the world and say negative things about your company. They discourage people from hiring your company, buying your products or working for you. And as former insiders, their opinion about your company carries considerable weight.

It grows revenues. If your company goes the distance, you’ll one day have more former employees than current ones. Many of these people will go to work for prospective clients or start their own companies. If you act like a tyrant when an employee leaves, imagine the awkwardness when you pitch your services to this person’s firm. But treat them well, and you’ll create a promoter who will advocate for you when you need it.

You might want to hire this person again, or hire people he or she knows. Sometimes the only way to move up at a company is to leave and gain new skills. Sometimes people leave because a unique opportunity emerges, perhaps to work at a start-up or with a new technology. Think about it: If you resent someone leaving, it’s probably because they were an asset to your company—and your company might yet benefit from their expertise (and demonstrated cultural fit) down the road. And don’t forget that friends and families of valued alums can provide great prospective new hires.

Treating departing employees well sends a good signal to remaining employees. Some companies still have security guards escort defecting employees out of the office like criminals. How embarrassing! If anything, the tone that sets keeps the revolving door spinning, spitting good people out rather than keeping the best people in. And worse, you imply to your remaining staff that you view them as little more than button-pushing robots (or traitors-in-waiting) who aren’t entitled to professional aspirations—let alone the right to be treated with dignity and respect.

It all comes down to this: Relationships matter. They are the basis for reputation—which really matters. Your professional path and those of your colleagues will likely cross and diverge again and again as technology makes this world smaller. Don’t let a bruised ego cloud your judgment when someone leaves. When that inevitable “hello” rolls around, that supportive, gracious “good-bye” will be worth much more than its weight in gold.