How work flow adhoc roles behave ?

Hi

I've done a solution to send some notifications. for each notification Im removing the existing CC list from the role and adding new user list to the role, but Ive noticed that all the notifications are sent to the last set of users.

As a workaround Ive created a new adhoc role for each notification and set the expiry date as sysdate+1. and my solution worked, but after few days users cannot see them from their work lists and all those notifications are not there in wf_notifications also.

1. Are the notifications removed from wf_notifications when a role expires?