You don't hear that expression as much these days. It used to refer to a man hitting his 40's and then doing something silly to prove to himself that he was still young, like buying a sports car or getting a young girlfriend. And it wasn't every man who succumbed to this condition, only the particularly foolish ones.
Even if "mid-life crisis" never quite made it into the Diagnostic and Statistical Manual of Mental Disorders, it was still considered an identifiable, distinct malady, not too dissimilar in nature to a "nervous breakdown" (whatever that meant).
This dread disease would almost always have its onset in a man's 40's (there was none of that foolish talk about how "50 is the new 35" back then). And it was assumed that the man would recover as soon as his sanity was restored, sort of like a patient being woken from hypnosis.
These days, you hear the phrase "mid life crisis" much less frequently, as people seem to have caught onto its real definition: being a guy -- of any age.
Most guys act in ways which would formerly have invoked the diagnosis "mid-life crisis" as soon as they can -- perhaps in their twenties. And even at the other end, age is less an impediment than it used to be. You might say that Viagra has encouraged "old age crises."
Exhibit A: Hugh Hefner.
Exhibit B: Silvio Berlusconi.
Do these guys look silly? Of course. Nonetheless, they look less so than their counterparts on the shuffleboard court at the retirement home.
The real crisis --no matter what your age is -- is not being able to act like Hefner and Berlusconi.
Our knowledge of psychology is dynamic and ever-changing. And we are far wiser than we were thirty years ago. We now know that to say that a male is having a mid-life crisis is somewhat redundant.