Being a man, but not 45-55 just yet, I understand what may be going on.
As men, statistically speaking, we mature later in life. That is not always the case though, just in general. Women tend to know what they want, and where they are going at a much earlier age. Given this age difference in a focus on life, men tend to get lost in thought and are more likely to readress their lives after 45.
With this, comes an interesting fact. We start thinking back to when we were younger, and the fun we did have or could have had. By the age of 45, most men are starting to think about their mortality. It concerns us a great deal. The realization that we are in the preverbial "over the hill", brings about a desire to fight the facts of life. Men tend to go after younger women. Not only to feel younger themselves, but in a way of saying that they are not too old. By younger, I mean 10 plus years younger than them. Our constant need to feel attractive and dominant drives this.
This has been mentioned before and I do think this is one of the big reasons why few men are interested in women their own age. Indeed women usually mature earlier in life, at any age. Just compare the average 14, 22, 30 40 year old woman and the average male in the same age group. There's a reason why girls/women usually have a relationship with a man some 2-5 yrs older. Even 15 year old girls don't want to get involved with a youngster their age, as they're still like kids. They go for the 18-19 year old as they're at the same level of maturity. And I think this difference doesn't ever really level itself out throughout life.
The problem I got at my age (47) is that men some 5-7 years older often look as if the best part of their life has gone. You can see it in their eyes. Many of 'em look spent. I'm too full of life myself, I don't feel the best part is over. I need someone who's still got "joy de vivre". I'd like my partner to be my equal, not my coaching & counselling client.
There are a lot of men who are MUCH more comfortable with women their age. Trouble is, that those men are secure with themselves, and typically are in what they concider a happy marriage. Though, I am sure that not all of them are in a relationship. Which means that there are guys out there looking for women their own age 45-55.
Sounds like the kind of man I'm hoping to find.