The term milf is much abused by porn - it seems it can begin at 25
A big part of that is that there seems to be no term between teen and milf other than 'pornstar'... and they're all pornstars
. I subscribe to the view that a milf is over 40 and a gilf is over 55... but I'm sure there will be disagreements.
I think porn falls back into the Indo-European Triple Woman archetype - mother, maiden, crone. However, our improved circumstances (e.g. health, life-expectancy and typical age of childbirth) have failed to account for the new fourth category between maiden and mother... the young woman. Blokes have it easier - Shakespeare gives us 7 Ages of Man... typical bloody Patriarchy!
Connoisseurs like Dreadder fall between the gaps - mother, maiden, crone translates sexually to a desire for fecundity, innocence or dominance; and petite women in their 30's aren't stereotypically fecund. As for other side-effects, too much domme porn is gilfy for my tastes, milfs are almost always voluptuous, and teens are typically small-breasted petites despite the many busty/chubby actual teens you see on a daily basis.
As a side-note: not subject to the Indo-European dynamic, Japanese porn goes heavy on the busty teen schoolgirls who lactate at the drop of the hat - interestingly combining fecundity and innocence. Weirdos
PS:
Fuck, it's easy to write Gender Studies stuff on the fly - almost like it's just a load of made up crap! 
I think porn falls back into the Indo-European Triple Woman archetype - mother, maiden, crone. However, our improved circumstances (e.g. health, life-expectancy and typical age of childbirth) have failed to account for the new fourth category between maiden and mother... the young woman. Blokes have it easier - Shakespeare gives us 7 Ages of Man... typical bloody Patriarchy!
Connoisseurs like Dreadder fall between the gaps - mother, maiden, crone translates sexually to a desire for fecundity, innocence or dominance; and petite women in their 30's aren't stereotypically fecund. As for other side-effects, too much domme porn is gilfy for my tastes, milfs are almost always voluptuous, and teens are typically small-breasted petites despite the many busty/chubby actual teens you see on a daily basis.
As a side-note: not subject to the Indo-European dynamic, Japanese porn goes heavy on the busty teen schoolgirls who lactate at the drop of the hat - interestingly combining fecundity and innocence. Weirdos
PS: