I have my character Honalee, who I started playing at a smidge over one year old, to my mentor character Roughshod (Bem's teacher), who is over 1500 years. And as soon as I can RP the birth of Honalee's brother, Peet, then I'll be RPing a newborn. Of course, it helps that Honalee is Nism (alien critter), and Roughshod is a Fyr Fyr (alien dragon). So, yes, as Brovo said, "it depends on the setting."

Indeed, I play Honalee as an adorably cute little girl, full of apparently boundless energy, who mangles the "English" language quite thoroughly. She's also what I'd term a "learning sponge". Whereas Roughshod, though I've never played him in an RP... well, I see him as being a very "grandfatherly" figure, well past his prime. Very experienced and wise. Not past learning new things, but far more likely to share his experience and wisdom with the young (like he does with Bem). A teacher, rather than a student. So yes, age should have meaning when it comes to how skilled a character is. Learning takes time.