About 10 years ago it took approximately 6 weeks to obtain a full history. That was also back in the day when requests were filed on paper.
Last summer, via electronic request form for DD214 only, it was received in less than 10 days.
It's uncertain from your post whether you are requesting the entire military history or status of discharge upon separation (DD214).
Here is the link that explains in detail what type of records are available and how to go about obtaining them:
http://www.archives.gov/veterans/mil...rvice-records/
Look around that site for other military links that may be of help to you. Read, especially, the paragraph pertaining to ""Emergency" Requests and Deadlines"
There are agencies that will charge fee to do what is available for free using the government's secure website (listed in the above link). Don't get scammed by any site offering to do it for you for a price.
Good luck and hope your son is reunited with all of you soon.