Guys usually have their first serious relationship between the ages of 19 and 21. Despite experiencing their first taste of love, they break up with their girlfriends around the age of 23 out of fear of being trapped.
They are out to "sow their wild oats", so to speak, between the ages of 24 and 29. This is just something that they have to do. Therefore, if you're looking for a serious relationship, I wouldn't touch any guys in this age range with a ten-foot pole unless you've found a diamond in the rough or your soul mate. This is when they are ripe for relationship training because, after all, good boyfriends are not born, they're made... By great girlfriends.
By the time they're in their 30's, they're hormones are a little bit more under control and they're ready to explore having a real relationship. They probably have the basics of a relationship down by now. This is their era of confidence. If they find the right girl, they'll date her for about three years and then propose. (Single men between 32 and 38 are especially hard to find because this is when they're in relationships that could potentially evolve into an engagement and then marriage.) Alternatively, if they haven't found a relationship they will continue to "sow their wild oats." As my friend Lulu says, "Mid-thirties are the new late twenties." This is why women in their late 20's-early 30's are either hit on by guys who are 26 or 42.
For the men who have been unhappily married, their passion usually wanes after 6 to 12 years, around their late thirties/early forties. This could result in a love affair or divorce. In their mid-40's, they mostly want to know that they've "still got it", especially with women in their early twenties. It's all very meaningless and experimental and they're fine with it. They will pretty much date anyone. That is, until they hit their late 40's, when their mortality is flashing before their eyes. And then they realize that they want someone to connect to, someone who gets them, someone who will love them. (If you're not sure how old a man is, check for wrinkles around his ears.)
By the time they're 50, if they're lucky, they will finally know what they want. They evaluate all of their past mistakes and learn from them. They want to wipe the slate clean and find true love, except now they're letting their heart guide them rather than their eyes.
Well, more or less.