Married for 43 years herself, she and husband her Charles co-authored "Golden Anniversaries" and "The Seven Secrets of Successful Marriage."

Schmitz shared some of their findings with staff writer Vickie Jean DeHamer. Here are some highlights of their conversation:

How many couples have you talked to?

Several thousand. They've been on five continents of the world. We've interviewed couples who've been married 30 to 77 years.

What has changed with marriage dynamics since the mid-1900s?

Part of it is the three most important factors in marriage modern couples haven't learned from generations past: If you look at marriage, it is really simple. The problem is people haven't learned or they don't know how, or they're unwilling to do the things to make love last for a lifetime. It's easy to be in love but it's hard work to stay in love.

Do people focus too much on the proposal and wedding day?

It's all about the dress, where it's going to be, who's going to be invited, and the moment of being in love. You forget the real beauty of marriage is that relationships last a lifetime. It takes simple acts of kindness day in and day out to build up these positive chips throughout the marriage that sustain you.

What are those simple acts?

Taking long walks together, cuddling in bed a little longer in the morning. It's all those kind acts and support for each other that these couples have done.

What has influenced what people focus on?

The mindset has changed primarily because of our Hollywood version of marriage. It's either a Cinderella story with no problems or no challenges, or we move on to a different partner.

What's the common thread you see in people married more than 50 years?

Our whole first book is about that research. These marriages really do have seven pervasive characteristics. These common traits are true no matter what continent you're on, whether you're rich or poor. Simple things: how you interact with each other and remembering this person is your best friend, and treating them accordingly.