So, these long-lived native outsiders are born to human parents. Since they turn adult in their 60s, what are the first 50 years like? Are they quickly maturing into teenagers and then exist as a teenager for their 20s, 30s, 40s, and 50s? Is every stage from toddler to adulthood slowed down? Do their parents typically spend their entire lives raising an aasimar to maturity?
Well, lets first deal with this how it was originally printed.
I would treat the issue the way you would treat a forlorn elf- ie- yeah, they take forever to mature, and that does make them separated from their peers (tieflings are shunned and have no roots, aasimar are put on a pedastle and practically worshiped, etc.).
Of course, the age categories were later changed...and made even more messed up. The starting ages were made more human... but the random dice were left with their original style (meant for century long lives).
This means that a the average tiefling wizard is 48 by the time they get their first level (20+8d6~20+28). But they still age and die at the same rate as humans. And note- from the trained age for humans, the average wizard is basically a college grad. So imagine a guy that took about 28 years to get their bachelor's degree, even if they worked at it. Note that they are just a couple years from entering the 'old' age category under these rules.
I know this is a slight bug....but even passed that, the numbers added on were still wonky. They start at age 20 (like half elves), but their new age categories are human based. So they are still 5 years behind the average human (that have a base of 15)
So that brings us from a mystical, long lived/late blooming race.... to something completely and utterly mediocre.
I know you can ignore all of this...but they went to the trouble of doing an official errata and they still messed it up on multiple levels. Making it worse when you took the time to fix it doesn't look good.
Anyway, you could just choose to ignore all this mess and just use half elf numbers. That is close enough to human to have normal story lines about people they grew up with, but you have later age categories so that your mid life crisis doesn't come until after you are 60.