Sorry, MacBeezle, but I'm afraid you're you're mistaken.
The ConnStore accounts can handle up to 6 devices per account, one of them must be a Computer (the one accessing the account). So you can put up to five Readers on a single account.
We've had a number of folks here in the past who have put two Readers on the same account, and gotten both credits. The credits are tied to the initial registration of the Reader on
any ConnStore account, it does
not have to be a new account, only a new Reader.
In fact, doing it this way is what Sony itself recommended, so that books could be easily shared amongst family members, etc.
This has been confirmed more than once, by several different folks.