Adsense more likely to reject because of content or more correctly LACK of Content than age.
(I have read and re-read adsense guidelines , and can't see ANY reference to 6 months).
No such thing as TOO much content so add as much as you can.
By content I mean TEXT articles , not RSS feeds or VIDEOS.
Use Feeds or Videos to Enhance the Text , not replace it.
Copy / Pasted Articles from Article Sites are actually OK if RELEVANT.
Also do not forget things like ad to content ratios ( Less ads than content) and Privacy Policy.
Most submitted sites are rejected because of simple easily solved reasons.
Remember your site has to be for USERS not a MFA (Made For Adsense) site.
Make the site look and work good without ads than add them later.
TOO MANY Minisites that are created have only 300 words of Crap content and 4 Ads.
People than blame google for rejecting them.
My most successful 1 page minisite with adsense has 1 [200 * 200] image ad only. It earns renewal fee weekly.
I have created Over 3000 minisites with adsense , only one ever rejected by google.
AdsenseSite.info << they didn't like the name (However it took them 4 years to complain).
Up to recently I taught a WebSite creation course , which included adsense usage.
NOT 1 of my students ever was rejected by google for their NEW Google Account / Adsense.
Most were accepted within 48hours of 1st day of course.
Only reason there seems to be bias against Indians is MOST Crap sites are done by Indians or other "Try 2 Hards" .
GOOD sites from anywhere will be accepted , CRAP is ALWAYS Rejected.