A decade or so ago, when a casino company was thinking about setting up shop near the Mississippi River tourist town of Kimmswick, Mo., I visited the Portland Place mansion of Lucianna Gladney Ross, the 7Up heiress who almost single-handedly had restored the town.

She was 86 years old at the time and unable to walk. She spent nearly all of her time in one room of her vast and stately home, a parlor furnished with books, a television, a bed and comfortable chairs. She told fascinating stories and vowed to keep the casino away from Kimmswick. For whatever reason, the casino was located upriver in Lemay instead.

Gladney Ross died last month at 96. I read her obituary — she’d correctly predicted 10 years ago that Kimmswick would be in the lead — and wondered if she’d ever gotten out of her parlor. That memory has haunted me — a beautiful 13,000-square-foot French provincial mansion on a private street, and she was stuck in one room. Big houses and living into your 90s might not be what they’re cracked up to be.

Last weekend’s edition of The Wall Street Journal featured a fascinating look at the mega-mansions being built by some of the famous wealthiest top 1/10th of 1 percent of Americans.

The size of the average newly constructed home in the United States fell to 2,392 square feet in 2010. The Journal was writing about homes that are 10 to 20 times that size and feature amenities like shooting ranges, bowling lanes, saltwater “plunge pools” and — my favorite — the 15-bathroom (plus powder rooms) home being built in Connecticut for Lee Weinstein, founder of Xand, a data storage company.

Fifteen bathrooms? I’m not sure how much is enough, but I’m pretty sure it’s somewhere south of 15 bathrooms.

The people who are building these homes are folks like you and me, except they’ve inherited a billion dollars or they are Saudi princes or NFL quarterbacks married to supermodels or they’ve built tech companies. Their wealth permits them to dream big when it comes to dream houses.

And really — what’s the difference between having one house with 15 bathrooms and having five homes with three bathrooms apiece? Will 15 bathrooms make you any happier than just one bathroom when you really need it?

So how much is enough? President Barack Obama wants to restore pre-2001 tax rates for households with at least $250,000 a year in taxable income. That’s enough, the president believes, to afford to pay more.

But in December, a Gallup Poll reported that Americans say they would need to earn a median of $150,000, or have $1 million in total net worth, to consider themselves rich. Thirty percent said it would take less than $100,000 a year to make them feel rich. Another 18 percent would be satisfied with $60,000 a year. But then 15 percent said they’d need $1 million or more a year.

Everything’s relative. The more you’ve got, the more you feel like you need. You’ve got a house with three bathrooms, you want more. You’ve got a house with outdoor plumbing — and in the 2000 Census (the 2010 data aren’t in yet) 670,000 homes still did — one bathroom is a dream.

But those data measure feeling rich. Is there no science for what is enough?

Sure enough, in 2010, Daniel Kahneman and Angus Deaton of Princeton University’s Center for Health and Well-being suggested that if you define “enough” as the point at which you tend to be happiest, the magic number is $75,000 a year.

They analyzed more than 450,000 responses to the Gallup-Healthways Well-Being Index, a daily survey of 1,000 U.S. residents conducted by the Gallup Organization. They looked at two aspects of well-being. One, how people reported their emotional reactions to everyday experiences, and two, “life evaluation,” or what people thought about their lives.

“We raise the question of whether money buys happiness, separately for these two aspects of well-being,” the authors state.

The more money you have, the more you tend to report being satisfied with your life. But beyond $75,000, there’s no increase in daily emotional well-being.

“We conclude that high income buys life satisfaction but not happiness, and that low income is associated both with low life evaluation and low emotional well-being.”

Further, they said, “Perhaps $75,000 is a threshold beyond which further increase in income no longer improved individuals’ ability to do what matters most to their emotional well-being, such as spending time with people they like, avoiding pain and disease and enjoying leisure.”

So while having a house with 15 bathrooms might make you feel more satisfied, it won’t make you happier than the very busy plumber installing those bathrooms for $75,000 a year. Just be careful not to wind up living in just one room of the house.

Kevin Horrigan is a columnist for the St. Louis Post-Dispatch. Readers may write to him at: St. Louis Post-Dispatch, 900 North Tucker Blvd., St. Louis, Mo. 63101, or email him at:

khorriganpost-dispatch.com.