I'd suggest:
How to handle cases when user adds
items of interest and never saves it
in a group before MOSS2007 session
times out?
Items are either stored in a local cookie, so they are there when the user logs in to MOSS again, or are lost.
How to handle cases when user adds
items of interest, saves it and then
adds more before MOSS2007 session
times out.
New items are either saved in cookie, or lost.
How to handle cases when user adds
items of interest, saves it, delete
some items from saved ones before
MOSS2007 session times out.
The deletion method should delete the records from the database. So they would be synced already. If however, you need a rollback option, you could do something similar to the Recycle bin functionality in MOSS...
Hope that helps.