I have had to deal with the 'age problem' as well... but more from the other end I suppose. Often I am summarily dismissed as being too immature based on my appearance and age. But I have learned to not be discouraged by this... often using this 'natural assumption' of people to throw them off guard. If they want to assume certain things about me because of something as misleading as age... so be it.. it does little to abate my ambitions and has often helped.
If I had not been this way I would've never caught my current bf's eye. He had initially dismissed me as being 'too young' and even stated that when we first met. After he had a chance to get to know me... he realized that I did have much to offer, despite my relatively few years.
I think you shouldn't worry so much about age or the 'cut-off point' that men have in their minds. In the end, a compatibility is far more important... and if it's there, then all else can be over-looked or accepted as a secondary/minor concern.
"The weakest soul, knowing its own weakness, and believing this truth that strength can only be developed by effort and practice, will, thus believing, at once begin to exert itself, and, adding effort to effort, patience to patience, and strength to strength, will never cease to develop, and will at last grow divinely strong."
- James Allen