I didn't gave my characters a specific age but the main (Akel) is in his lates twenties, the two others important characters are mid thirties (Matten) and early forties (Kyrim).
My story has been going on since the characters were teens, currently they're in their late 20s, some in early 30s. One guy is 35ish and he's been in the story for.. uh.. 18 years.
A few parents also show up, although infrequently, who have also aged, so now are 50+.
At some point a whole different dimension and a space ship was discovered, so everyone who went there acquired an additional age counter due to different flow of the time. Most people from that spaceship start their lives at what counts as teen years on Earth. A few characters have lived for a few centuries on there but would've been 50ish on Earth, like a certain female anti-hero. (Yes, I have an older female anti-hero and she's great!)
That is tricky for me I can tell about the humans but about the demons is not that easy. well Roger is 26 and Voluptia's have the looks of a 22 but in fack she is 15000 years older than that since she was one of the fisrt daughters of Lilith. The Doctors is 48, Sister Paula 24, Father Thomas is also 26, Sarah is 17 almost 18, and Luciano 19. The colonel Whult is 52. Ambrosius nowadays is nearing his 80s and mother Ana is 76.
My characters usually tend to be around my age just because I find it easier to write out how they would act without it coming off as weird. It's also easier for me to give them problems that I can... relate to I guess? Because I know what it's like to be that age
The main cast in Finding Haven starts with Mags being 16/17, Ezra and Avi are both 19, and Myriam is 21! The last 3 were actually a lot older when I first created them but I just kept lowering their ages as the story developed haha
The character that was supposed to be the main character of my Oh. My. Fate?! series (Jing Yi) started out as a newlyborn. Well, that kinda led to the male lead, Qiu Ling, having more chapters than him so the readers tend to regard him as the actual main character 
Jing Yi did grow up over the volumes until he finally reached adulthood in the fifth volume though and has a lot more chapters dedicated to him and his actions now. I still feel like this cost him the spot of main character though
The main characters of my series are 15-16. The oldest (human) character is 46, and he is quite important but isn't in the comic yet.
I stopped being a teenager years ago, but somehow I still write mostly about teens. Probably because I'm emotionally immature and weep over my lost youth. ¯_(ツ)_/¯ Also I feel like characters notably older than me would be harder to write as protagonists?
Though, from my experience writing teenagers during your 20s is quite different from writing them when you're in your teens yourself - you're more emotionally distanced from typical teenage problems and know that these aren't always things that will matter in 5 or 10 years.
Hmmm, I should try writing a main character over 20 at last...
I don't have art on me HHHhhhH
The dark lord (Chick in purple robes pretending to be a guy)
Is around 500+ years in our world (half an "age")
In world, I'd imagine the characters referring the intombed dark apocalypse as around "5C"
Physically she should be 17, but pretends to be like 30 and intimidating, though take that with a grain of salt because mentally she should vary having time travel xD
Her eldritch buddy should be since the beginning of time, and before, only achieving its latest iteration of sentience 500 years prior.
The characters in my story are immortal, so my mc is 87 years old! In actual understandable human years i'd like to think he's 29, but looks are deceiving because I have such a squishy/cute art style. He stopped aging in appearance around 25.
Most of my characters are close to me in age (early 20s) because I know that voice so well and its in my comfort zone.
Right now I’m working on a comic where the main protagonist is a single mom late-30s with a teenaged daughter. I think I’m comfortable writing these characters having grown up with my single mom as a teen.
My 2 main characters Roxy and Ron both start off at the age of 19 in the beginning of the story. Since there's some time progression, they are both around the age of 24 in the present day portion of the story.
This post was flagged by the community and is temporarily hidden.
Laila is ambiguously 18-21 years old.
As for the titular Eli...without spoiling too much, he's mentally about 30. Or maybe late 20s, IDK.
My main characters are teenagers. Gother is 19 years old and Violetta is 17 years old.
But in the comic will appear a few characters at the age of 40 and more (families of main characters)
The comic I'm working on is about university so most of my main characters are 18 years old and in their first year. Zoey is in her final year and 21 years old. Of course the teachers and lecturers run the gamut age-wise but I'm still working on fleshing out the supporting cast.
This forum thread has me thinking about the exact ages of main characters. I've never thought about the exact ages, since the story takes place in different time periods.
Right now the main character is 0 years of age, since he hasn't been born yet.
Larry and Christopher are some where in the age range of 10 to 15 years of age.
Alexander, a warrior cat from a different planet, is some where in the age range of 30 to 40 years of age.
My characters range from 18 to 60 something in knight´s song
Main character Gerard is about 18 and his father in he´s sixty's or so!
link1
Let's see, well:
Po: 10 yrs.
Casiea: 10 yrs.
Miara: Physically 8 yrs. but several thousand years old
Zee: 22 yrs.
Rose Remington: 17 yrs.
I really like characters who are older, I feel the same in that they just don't get enough exposure. But you're right in that it's just not common.
We write comics with characters that are older than us, for the most part, but still sometimes around the same range that you mentioned.
The two main characters in Mal de Ojo are around 35 - 36
In Love Labs, they are around 35 and 38
An old comic I was working on had main characters ranging from 11 to 65 and 70 (The older characters have a lot of backstory and aren't just there to grow the story of the younger characters hah)