Even if spammers aren't using old accounts, if something like that was implement...

seancron on Nov 3, 2010 | parent | context | favorite | on: "Rate My Startup" Post Policy

Even if spammers aren't using old accounts, if something like that was implemented, spammers would just add

  sleep( n * 86400 )

to their bots. Once those n days were up, there would be yet another wave of spam.