This has been discussed in the past but the Admin decided the 45+ and 45 and under room was the best way to go as neither room gets a lot of traffic.
The creation of additional separate rooms is problematic, because there are all sort of cut-offs to consider to be fair to all members. Should there be rooms for under 30, a 30-40, a 35-45, a 45-55, a 55-65? Then you get into the problem of too many rooms again.
While things may change one day, I would not be very optimistic about the prospects of adding additional forum rooms. Having said that, there is nothing preventing the 55+ or the 65+ crowd from starting individual threads within the 45+ room. For example, while there are exceptions, most people in their late 40s are not retired, but most over 65 are, and thread titles like "Have you travelled with a seniors group tour / gone on a seniors cruise?" or "What do you grandchildren do or say that makes you laugh?' are aimed at an audience with more life experience.
First, I am "37 and holding". White knuckles, perhaps, but if CM's system didn't require it, my age wouldn't be on here.
Second, in my experience, for women, at least, there's no difference between 45+ and 55+: you are still dead in the water.