For Americans looking to retire abroad, deciding where to live can be a challenge. But Lynne and Tim Martin took that question off the table by deciding to retire everywhere and anywhere.

In 2011 the couple opted for what might be called extreme retirement abroad: They sold their Paso Robles, California, home, jettisoned all but a few treasured possessions and became nomads.

Since then, they have lived in short-term rental apartments and houses around the world, usually found through HomeAway.com, the online vacation rental service. They spend two or three months a year in the United States, where they also live in vacation rentals.

So far they've lived in Mexico, Argentina, Turkey, France, Italy, Britain, Ireland, Portugal and Germany. Southeast Asia, Australia, French Polynesia, Canada and a return to South America are on the agenda.

"I just felt strongly that I hadn't had enough of the outside world to suit me, and really wanted to go experience living in some other places," Lynne says.

Lynne, 73, is a former publicist; Tim, 68, owned a small electronics business and writes novels. This year they published a book about their experiences called "Home Sweet Anywhere: How We Sold Our House, Created a New Life, and Saw the World" (Sourcebooks, April 2014).

As the Martins talked about how they could forge a footloose lifestyle, they decided to tap the wealth built up in their home and possessions.

"We had a portfolio, but not a huge one - we're not wealthy," she says. "We took the money out of the house and added that to the portfolio."

Their financial adviser sends them the same a $6,000 monthly stipend. they had been receiving as California homeowners. They live on that plus their Social Security benefits.

They aim to spend no more than $2,500 monthly on housing, including utilities and cleaning. In a pricey spot such as Paris, they'll downsize the amount of space they rent. They also figure on $1,000 for food and $500 for entertainment and travel. The rest is for miscellaneous expenses.

Since Medicare doesn't provide coverage outside the United States, they see their doctors during visits home. If healthcare needs come up while abroad, where care tends to be less expensive, they pay out of pocket. While they're outside the United States, they also carry an international health insurance policy to cover unexpected large expenses - $400 a month.

One way they've kept costs down is by limiting the amount of travel. They tend to stay in one place for months at a time, often scheduling travel at off-season prices.

One favorite tactic: off-season "repositioning cruises." "Prices go down by half, and it's great for people like us who don't have a home - we get room and board as well as transportation."

"We went to Europe in February last year," she says. "It was snowing in Venice when we arrived, but it didn't matter to us - we weren't coming home until October."

STORIES AND FRIENDS

The Martins have four daughters and seven grandchildren in California, Texas and Florida. They are in the United States at least twice a year, and make a point of seeing the entire family while they're here.

"We're much more interesting to our grandchildren now," she says. "They find our stories of Morocco, Istanbul, Paris and Buenos Aires fascinating."

Martin says they stay in touch with old friends via e-mail and Skype. "Those relationships are as strong as ever," she says. "Some friends came to visit in Paris this past summer; it was a treat to share our favorite places with them."

And they've made many friends on the road, some of whom they meet up with in their travels.

"It's a curious bond that travelers have - we seem to get to know one another much more quickly than we would in traditional circumstances," Lynne says. "We've met up with our German, Mexican, British, American and French friends in other countries by coordinating our travel schedules."

I wondered if all that travel isn't tiring, and how long the Martins expect to keep up their nomadic lifestyle.

"Of course we get tired - we're old people," she says. "But the life we live has built-in rest. We're not staying in hotels - we're in places with a living room, kitchen and bedroom, real living space.

"We're able to have down days in a way that tourists really can't. If you're only in a place for five days, you have to get out and see it. If you're there a month or two, you can put up your feet and stay home all day."

The Martins say they'll keep traveling as long as their health permits.

If nomadic retirement appeals to you, Lynne recommends starting with a trial run.

"We're lucky because we're so compatible and we have a good time with one another," she says. "But a lot of people may not understand how you have to depend on one another when you're in an isolated situation and don't speak the language.

"Rent your house out and go off for a few months to see if it's for you."

(The opinions expressed here are those of the author, a columnist for Reuters.)

For more from Mark Miller, see link.reuters.com/qyk97s

(Follow us @ReutersMoney or here. Editing by Douglas Royalty)