E.g., "The iTunes Service is available to you only in the United States, its territories, and possessions. You agree not to use or attempt to use the iTunes Service from outside these locations. Apple may use technologies to verify your compliance." - http://www.apple.com/legal/itunes/us/terms.html#SERVICE
The system is also not set up for frequent switching between accounts for the purposed of redownloading. You have multiple accounts so you can get around the country switching wait period, but as a result you are working outside design parameters. I could see where frequent reauthorization is made difficult so as to prevent people from going over to a friend's house, logging into their account from their friend's computer, downloading all their purchases onto the friend's computer, then the friend logging back on immediately. etc.
iTunes Store: Associating a device or computer to your Apple ID - http://support.apple.com/kb/HT4627 - In connection with, "When you turn on iTunes Match or Automatic Downloads, or when you download past purchases on an iOS device or computer, that device or computer becomes associated with your Apple ID." "Your Apple ID can have up to 10 devices and computers (combined) associated with it. Each computer must also be authorized using the same Apple ID. Once a device or computer is associated with your Apple ID, you cannot associate that device or computer with another Apple ID for 90 days."
Normal use of a single account or on a computer that is properly backed up so repeat downloads are not necessary will avoid the authorization issue. Since you are kind of working on the edge of how accounts are designed to be normally used you will have to ensure you have your content properly archived on local drives so you can avoid having to frequently redownload.