Guy,
We have a similar requirement: keep weekly backups for 1 month, monthly
for 1 year.

1. Yes, you must use different management classes to get different
retention, but...

2. You can't backup the same data to different mgmt classes because
what's already on the server will get rebound to the new mgmt class...
For example, in my environment, when the monthly backup runs, all the
existing weekly backup versions would be rebound and kept for 1 year,
then next week, everything would be rebound again and kept for 1 month,
etc... SO...

3. The only solution we could come up with is to have a DIFFERENT NODE
defined on the server for EACH DIFFERENT RETENTION REQUIREMENT.  For
each client, we have a CLIENT node and a CLIENT-MONTHLY node.  The
monthly management class is defined in a MONTHLY_DMN domain and the
CLIENT-MONTHLY node is in that domain.  Since ADSM server thinks it's a
different client, no rebind.

Hope this helps...

Robin Sharpe
Berlex Labs