It's a two part
The whole domain age thing. If a site is blacklisted, requested a reinclusion, does this affect the age factor? ie. loose it?
Buying two domains eg. www.example.com & www.exampletwo.com
If both domains where registered at the same time, but you have only been using www.example.com to host the site, will the www.exampletwo.com have any "domain age"?