zfs discuss - Jun 2011 - timeslider autodelete -vs.- my retention goals

Hi,
         I''m trying to do a simple data retention hack wherein I keep 
hourly, daily, weekly and monthly zfs auto snapshots.

To save space,
I want the dailies to go away when the weekly is taken.
I want the weeklies to go away when the monthly is taken.


 From what I''ve gathered, it seems time slider just deletes the eldest 
snapshot when there''s space contention.  Is there a simple way to alter
its logic to achieve my retention goals, or must I just write this logic 
myself?

thx
jake