Never, unless I work with them or am direct friends with them (as opposed to them being my parents’ friends, or parents of my friends, say). I’m 37 and one of my good friends is maybe 34 and I still feel compelled to call her parents Mr. and Mrs. So-and-so. I met them when I was maybe 25 and it stuck.
I always used first names. My parents are Quakers and they believe in that sort of thing. That, plus growing up in Australia, makes me suspicious of anyone who doesn’t do it and encourage it in people of any age outside highly formal situations.