Lori and Marek Fuchs have never fought in their 16 years of marriage—except over money. In this column, Mr. and Mrs. Fuchs, a real-life married couple with three kids (ages 12, 7 and 5), articulate their very different approaches to personal finance.

This round the Fuchs mull just how long "til death do us part" actually means.

Mrs. Fuchs: You know that joke I always make about you having to work until you are 80?

Mr. Fuchs: Yes, it’s not so funny.

Mrs. Fuchs: Well, I just read an article that said with medical advances, life expectancy is rising rapidly. Do you think our plan for retirement takes that into account? I’d hate you to have to apply for jobs when you are 95!

Mr. Fuchs: Now you’re killing me.

Mrs. Fuchs: Seriously, when people used to think about saving for retirement, it was for a limited amount of time. You retired at, say, 65 and died a few years later. Now, eat lots of vegetables and walk 10,000 steps a day and you can live to 100.

Mr. Fuchs: I personally don’t even plan on dying. But how do you plan for a retirement that long and who do you talk to about how many total years you should save for: a financial planner, a doctor or a priest? How do you know how long you are going to live? It could be 100, or you might get hit by a bus at 65.

Mrs. Fuchs: Look both ways.

Mr. Fuchs: I even look up to make sure nothing is going to fall on me, but who knows how long we are going to live? What a financial, genetic crapshoot, huh? Where do you start? We have young readers like 26-year-old Anthony Nugnes, who lives in the DC area, and is expecting to live to about 80. But considering drug technology, that dude might make it to 140…

Mrs. Fuchs: If he looks before he crosses…

Mr. Fuchs: Right, but Anthony wants to stop day-to-day work by 50 and my friend Michael Lombardi, who worked in finance for decades, points out that if you spend a lot and want to pay for your own funeral, you might have to keep working until shortly after your death.

Mrs. Fuchs: Doesn’t it also depend on what kind of job you have and what the benefits offer? My parents were able to retire early with great pensions until the day they die, but we’re both self-employed – how do we figure it out?

Mr. Fuchs: Yeah, your parents were teachers. In terms of lifelong pensions, they are essentially "The Last of the Mohicans." For the rest of us, it’s the most important guessing game we’ll ever play.