I don't think it's just
a matter of perspective or association. Perfumes released during certain eras participated in the trends of that era. So if by "mature" you mean "something that smells like it was formulated before the 70's," then I'd say certain treatments of aldehydes, ambers, musks, and galbanum are "mature." Vintage isn't my thing so I can't roll examples off my tongue, but... I think you'll know it when you smell it.
Now if by "mature" you mean "more suited to an adult," I agree it's up to a fragrance's complexity, depth, and strength, but I also think that it depends on how wearable
a fragrance is. Like, I think Annick Goutal Petite Cherie is (by design) a great example of a young fragrance because it is light and floral and inoffensive; anyone can wear it. On the other hand -- I mean, just to compare something from the same line -- Mandragore is herbal and citrusy and a bit dark, so it's not exactly something everyone can pull off; I think one would need more character to be able to wear it. Maybe character = maturity....
You know, the various incarnations of Chanel No. 5 are a good demonstration of this whole deal. Try comparing the current EDP versus Eau Premiere, see what you think of each.