There are two type of aged accounts.
1) Real aged accounts who continuesly intract with fb post, do like/share/comment/ daily or weekly - That kind of accounts will help you to prevent instant bann(Not for lifetime, because we are doing spamming, and no matter who the hell are you, they will bann you, but for aged account the spam filter need more signal to disable your account)
2) Just created aged account to sell - There are many of service, who just create fb account and sell it after 2 years and there is no much acitivity on those accounts, so those account will get bann soon.
I personally help my local friends to grab someone fb accounts, and I got daily many of in cheap price.