I've been advising young male colleagues at work not to date older women (over 30).

From an investment perspective, the scariest thing about leftover women isn't their age, how many boyfriends they've had, or their cohabitation history. It's this: they want to recoup their losses - the older they get, the stronger this mentality becomes. What losses? All the setbacks they've suffered over the years. They'll try to recover everything through marriage. So, cherish your life and stay away from leftover women.