Financial advisor Scott Hanson said his clients have been asking him why they need to retire "just because [they're] 65." There's been a shift in mind-set since 2008 due to economic realities and people living longer, said Hanson, a certified financial planner and co-CEO of Hanson McClain.
"We're having many more of those conversations now, especially with clients in their 50s who are unhappy with their jobs," he said. "We ask them: 'Why live like that?'
"A lot of people are marching toward retirement because it's what they're supposed to do, not what they want to do."
In fact, a recent AARP study found that 37 percent of working Americans age 50 to 64 plan to work after retiring from their current careers. Of those, 44 percent intend to enter new fields.
Hanson is seeing more and more post-retirement career changers, including:
"Clients often think they want to get rid of responsibilities, but we're happier when we're needed," Hanson said.
Beyond being needed, architect/consultant Steve Sunderman is happiest when he's working.
After a 40-year career of moving to different jobs across the United States and in Saudi Arabia, he left his final position as partner at an architectural firm at age 62 to start his own company, Terrazia PC, an environmental and energy conservation consultancy.
"I've never been afraid of making a move," he said. "I could have stayed on, but I wasn't excited anymore. There wasn't enough autonomy," he added. "I wanted more control, more design work and more 'green' projects."
Sunderman said his wife told him he was crazy. "But I'm not afraid of change," he added. "I love new challenges."
Soon after he went on his own, he scored a major contract and has continued to grow and thrive over the past five years. Sunderman's advice to later-in-life career changers:
"As my clients age, I hear more and more of them say, 'I want to follow my dreams," said Robert A. Karn, CFP and principal at Karn Couzens & Associates.
But to start a second career, you have to have a very different mind-set than most retirees, he said.
"You can't touch your [individual retirement account], and you may be giving up a secure income stream for a number of years earlier than you have to," he said.
Financial planning for these clients will need to include revisiting cash flow, risk tolerance, tax management and Social Security strategies, Karn added.
Nevertheless, Karn said he tells clients to "do it while you're healthy — before you hit that brick wall and you can't do what you want."
That brick wall was on Carol McSweeney's mind when she decided to forgo traditional retirement to become a full-time artist.
After a 30-year career in special education and school psychology, she decided, at age 53, to throw herself full-time into her new career. McSweeney seemed to have been following some unseen path.
In the course of her work as a school psychologist, she had used art to help abused children express themselves. She took the first art class of her life when she was in her mid-40s. Several years later, she took a one-year sabbatical from her job to study in Australia.
"I had intended to study art therapy, but they closed the program when I got there," McSweeney said. "By word of mouth I found evening classes that incorporated art therapy and art training in narrative art, and it was there that I realized that's what I was supposed to do."
After retiring and consulting in education for a few years, she said she felt a pull and made a decision.
"I realized that unless I put my art first, this career wasn't going to happen," she said. "I let my educational certifications expire,, and I remember thinking, Am I losing my mind? But this is who I am and I need to commit to it."
Soon, McSweeney had as much work as she could handle- and her income has grown continually since she began nine years ago.
Her advice to others considering a later-life career change?
"If it's integral to your well-being and who you are, just do it. Every step I took convinced me I needed to stay on this path."
— By Deborah Nason, special to CNBC.com