It is my understanding NCMEC does age progressions for missing children every so often. I've read they do them once a year for younger children and every 3 years if the missing child reaches adulthood still missing because the changes aren't as drastic. (can't confirm that as being 100% accurate, it is just what I have read.)
There is a site, phojoe, that does both age progressions and age regressions. I found this several years ago looking for information for another case. There is a fee associated with ordering age progression photo's.
Perhaps, Solomon wishes to have age progression photo's done of Sky on photo's he can verify the date and he is comfortable/confident with having confirmed the actual date. I can't blame him for questioning the accuracy of the dates of certain photo's. He's the father of a missing child whose mother is providing zero assistance whatsoever. If he wishes to have aged progressed photo's, I fully support his doing so. It won't hurt for him to have that information and decide on whether he wants to make them public.
Here is the link for the site which provides age progressed photo's at a fee for their customers. I don't know if they provide services at a discount for parents of missing children. That is something for those closest to Solomon and working directly with Solomon to look into themselves. There is one age progessed photo of missing adult Cynthia Day age progressed to age 53. Her daughter either posts here at WS or is in contact with members working her mothers case here at WS, and commented about her mothers age progressed photo at the site.
http://www.phojoe.com/forensic_compositing.html
hth