Older domain names, provided they haven't been overly spammed out, have already established a certain degree of authenticity and credibility with the search engine. After a content overhaul they wouldn't normally require any probationary period to ascertain rank.
I agree that Google trusts the aged domain name more than a newly registered one because they have been around for a while. Alot of factors and way to find and purchase aged domain names with a good price, you can purchased old aged domains from different sources as long as they are reliable and has the list of high standard aged domains. I recently got mine from domainka.com and godaddy.