This sort of math always breaks down. In a year or two, it will hold up less. In 3 or 4 years, it will not matter at all, largely because of the sliding time scale.I think as of right now his official age is 29, since he became Spider-Man when he was 15, we know Spider-Verse happens 12 years after that, and there has been at the very least 2 years since then, because of the whole 8 months between Secret Wars and the start of Worldwide, and then the year Scorpio is locked away.
(That is simply the nature of comics.)
2013 was more or less the last year that the old 4:1 rule (4 years of page time : 1 year of real time).
Which "side" of a time-skip something happens on can help to telescope events. (IDW's "Transformers" comics used time-skips to cover the natural lag of monthly comics. For example, a three year time skip actually "covered" a year-long series that was actually set over the course of a few weeks, and a good chunk of the next series. IDW actually kept real-time for ~7 years. But, that takes editorial discipline, and they abandoned it.)Slott stated “13 years later” after Spider bite in the relaunch issue after Superior. So he was 28 at the rise of of Parker Industries before Secret Wars. Safe to say he is at least 29 by now. I have a feeling the time skips around Secret Wars could be retconned to be shorter.
Changing sensibilities are another problem, beyond the question of "how much stuff can possibly happen to a character in ~15 years"? This sort of question is why hard reboots can be healthy. But, hard reboots, or even fuzzy changes (for example: swapping out ham radios for laptops) require changes that some fans cannot accept.That means that Peter now Post-OMD was born in 1988-1989, the year after ASM Annual #21 IRL, and he got bitten by the spider three years after 9/11, which means he MJ and Gwen hit their college years around the Obama Presidency and the recession...can you imagine what that means. How does Goblin dropping Gwen off a bridge, you know lunatic flying around Manhattan on a glider look in a Post 9/11 era...
This is probably why Quesada has pushed against the idea of a strictly cohesive universe. (What would we rationally expect the NYC of Marvel to look like, considering everything that happens there in even one family of titles, never mind everything.) But, again, comic fans cannot accept this.
Miles reads like an outlier for that generation, being smarter than average. (Most teenagers, of any generation, are not as tolerable as Miles.)Whereas Miles Morales does feel like, read like a member of Generation Z, and going forward he will have to be the high school kid of each generation, which is going to be harder to do but not impossible.
Writing kids is difficult. Even if the writer can pull it off, the audience is likely to misread it. (DC's Jason Todd Robin was probably the most realistically written kid character in comics. But, it was misread as "the character is a snotty little punk at best, and probably a psychopath" rather than "he is a damned teenager, of course you do not like him". That misreading has since been validated, and defines the character long after he has aged on-page).