My mini, Sanyu, is 18. Her mom is going to be a mini, too. (I'm determined that they'll match... ) So I guess my own are/will be viewed as adults. Personally, though, I think it all depends on the type of doll you get. My Sanyu is a MNF with a large chest... so she looks more adult. Other models look youner, like preteens. Some look even younger than that. I have another character who will probably be a mini in the far-far distant future... and I'll probably do the 13 year-old version of her. So I suppose it all depends on the doll.
My mini's are adult's trapt in children's bodies... except my BB Sprite who is actually a little girl, 12 years old. And my two ghosts who died when they were children but have been around for centuries, so they act like adults.
Compared to my SD girls, I have a hard time imagining any MSD-sized dolls I'd have as anything older than 12. Mature minis throw me for a loop since I want my dolls to have a size/age continuity between them. Currently Renee is a very tiny 13 year old, but I'm working on getting a less developed body for her that better suits her character and height.
Rion and Lilia (both DoCs) are about 14 in age. Rion's twin, Cain (when he gets here *squee*) will be 14 as well. That's why I trust them all together at night, they may be curious but they're too young and nervous to do anything but cozy up to each other. ^_~
I have an AR Present Jade 01, Kid Delf Ani boy, and a Bobobie Tony. All are in their mid to late teens (my Jade is the youngest of the three). I don't see them as having to be in scale with my 60cm, so I have no need to make them children. A lot of how old or young a doll looks has to do with faceups, wigs and clothing.
I have a kid delf ani, and she is 12, she has a bit of a baby face and an immature body. My Unoa Lusis has a much more mature body, and is a precosius 15
My minis are both Minifees with pointy ears, so they have mature bodies and are both grown (well, late teens-ish). I just write it off as them being a different "species", so that's why they're smaller than my other dolls. ^_~
All three of mine are mature minis (minifee), so I'd estimate that my Shushu twins are around 19 years old, while my Lishe is about 21. Kinda hard to think of them as anything but adult when they're so... er... filled out.
Like many others wth 'mature minis' my Lati Blue Yern 'Tuppence' is definitely a young adult to me. She has always seemed more like a young woman in her early 20s, though I suppose she could just scrape in as very late teens.
My mermaid girl MSD (see avatar) is a child of about 10 years old (in mermaid years, whatever those might be). This is my favorite age, one is smart enough to have an effective mental presence, yet unaffected by dastardly hormonal adult problems. XP Raven
Even though DOC's aren't really considered minis with mature bodies, my Kirill's age ranges between 12 and 14 ( I can never really tell his exact age ^_^; ) while my Ivan is 17. My other mini, an Angell-Studio Gus, while his body is a bit taller and slimmer than my DOC's, he is 15-and my 'in-process' Latidoll Ryu ( with DZ Body ) who has a more mature face-sculpt will only be 15 as well. I guess in my opinion it doesn't completely fall on whether or not the sculpt is considered mature or not either, but moreso really, what age is the dolls character? I know this probably doesn't work for everyone, but suits me just fine x3
I think of my DZ Shoyo as being 19 and my DOC Twing~Key as being 18. So just at the end of their teen years.
I think my slim minis as teenagers. My Narae, MNF and Minisupia are about 16, and N-doll Miso (who is slightly smaller and looks younger to me) is maybe 13. Then my PW Mori Moth, who has an immature body, is about 9. Of course she's not in scale with the other minis, as they are all about the same height, but it doesn't matter since she belongs to a different 'storyline'.
I see all my minis as late teens, early 20s. My Unoa Mocha is mid-twenties. I tend to dress them older too.