Louise and Martine Fokkens, two 70-year-old twin sisters who have been prostitutes in Amsterdam for over 50 years, have decided to retire. They estimate that they have slept with about 355,000 men between the two of them. The twins are confident their income from film rights will keep them solvent in the years of retirement ahead.

Louise and Martine are believed to be the oldest prostitutes in Amsterdam, and possibly the oldest in the world. Last year they starred in a documentary film called Meet the Fokkens. A New York Times review of the film concluded that beneath the Fokkens' cheery facade lies a familiar story of poverty, male violence, abuse, childhood abandonment and a struggle for survival.

Louise, the mother of four, said that due to her arthritis, some positions are now too painful, while Martine, mother of three, complained about a drop in customers. Only one elderly man, addicted to his weekly S&M sessions, remains a regular, she said. "I couldn't give him up. He's been coming to me for so long it's like going to church on a Sunday," Martine added.

Given their experience, they do offer an interesting look at modern shifts in the world's oldest profession. Brothels were legalised in the Netherlands in 2000 - but the sisters say this has not improved prostitutes' lives. "It is better for the pimps and the foreigners, but not for the Dutch girls," Martine said.

In February 2013, Amsterdam raised the minimum age for prostitutes from 18 to 21. For Louise and Martine Fokkens, though, it's the maximum age that's cause for concern. The 70-year-old sisters had been thinking about retiring for some time.

The Fokkens recently finished a new book on their sexual endeavors, "The Ladies of Amsterdam," and say it's time to hang up their stockings for good.

What do you think about these 2 senior citizen working girls?