Seriously, wtf is a "mature" woman?

I'm sure this isn't the first time this debate has come up. I see chicks on "mature" sites and on the site they list the girl as being 29 years of age. Personally, I don't consider a woman mature until she is AT LEAST in her mid 30's. I've tried to promote mature sites but I guess I'm completely out of touch with what people are actually looking for in this niche.

So I ask you this question. When Joe Snuffy porn surfer gets on his computer and decides to go look at some mature pussy, what the hell is he actually looking for? Chicks in their 30's? 40's? Older? At what point does she stop being a mature and becomes a granny? Because just like matures, I see so called "granny's" that don't look at all like what I would consider to be a granny.

Last but not least, can someone spam me with some "mature" sites that they've been able to convert consistently? I've tried a ton of different sponsors and I've gotten sales from several of them, but at the same time I can't seem to find a single sponsor that actually sells with any kind of consistency. It seems that I just have no idea what the fuck I'm doing when it comes to this niche, so maybe one of you can set me straight.