I would expect BDSM to be the best place to be if you can no longer be classed as young-and-beautiful, for the same reason that it's a good place to be if you are plus-size, differently abled or otherwise non-standard. (All my best subs have been at least one of the above.)
Things are confused because BDSM overlaps very much with the fetish scene, whose porn is even more than BDSM focussed on Barbie figures. But even there, in real life rubber or vinyl fans are just as likely to be large or old and not ashamed of it.
Every so often someone asks, more or less challengingly, "Why are there so many fat women in the BDSM scene?" And my own answer is that because BDSM is so much about what you do and what is going on in people's minds, looks don't matter the way they do to vanillas. A good slave is judged by the depth of her submission, not the height of her breasts.
The same should - and in my experience, does - go for age. And that's only subs: for Dommes, I would imagine that one of the wonderful things about the role is that as you get older you get better placed to project dominance and command respect.
By the way, I would be interested to hear again from the original poster. Is your particular interest in dominant or submissive older women? What situations do you like to see them in?