For now, I'd leave it well alone and see how things work.
If they don't work, ask again with more details.
I think (not sure) that once the authorization has been made to the underlying AdobeID, that authorization remains.
The device doesn't recheck the current password (or even the current email) associated with the AdobeID,
and things just go on working.
I had to change my Adobe password recently (after the breach in the Adobe security)
and didn't change anything on either my Sony device or ADE.
There shouldn't be an issue deauthorizing and reauthorizing if you do need to.
Of course, you will need the new password to reauthorize.
The Adobe infrastructure should keep count properly and know you haven't added an extra device,
but if it doesn't you may need to contact Adobe to get all your authorizations reset.
Post back if that seems to be an issue.
If you use Overdrive library books, you will probably find that ADE2.0 does not work correctly with the Sony.
In that case, replace ADE2.0 with the older but much more reliable v1.7.2.
There are lots of bugs in ADE2.0 (and 2.0.1). Try replacing ADE2.0 with the older but more reliable v1.7.2.
(You can have them both installed at once if you like.)
Version 1.7.2, it is a little difficult to find, available on Adobe site for Windows and for Mac.
The forum software is sometimes corrupting the link above. There shouldn't be a blank in 'editio ns.html'. The following redirects to the same page: http://tinyurl.com/diged172
Thank you so much. I had wondered if that would be okay just leaving it so I will run with that first and see how I go. I will keep a copy of your suggestions in case I need to revisit at some stage. You obviously know your way around all of this!