Thank you Christoph! So... which alt account are you posting from? A newbie account that can write detailed explanation on something technical.
As long as you don't use the Satoshi-Client or another non-deterministic client to spend the coins on these addresses you don't need to back the keys up again. The other client's wallet IS in fact a backup, you can spend funds from the imported keys as well as from the "original client".
The Armory wallet backup does NOT contain keys imported later, but writing down each imported key and safely storing the paper is sufficient as a backup. Keeping the wallet on another storage where the key was imported from is also a backup.
I understand that Armory's wallet does not back up the imported keys. If I installed Armory then imported all keys private keys from Bitcoin-Qt wallet, but now I want to install Armory on a second computer and load the same Armory wallet from the backup; is there a way to not have to re-import all the non-Armory keys if I still want the other address from Qt that was already on the first Armory install? I guess just copying and pasting the whole folder would be the best option of I want a duplicate copy on another computer?