I consolidate all tracks to the same length from the beginning of the session, and dump everything else. When I do this, most 48track songs are around 1.5 GB. O got the last record I did (all ten songs, all tracks, average of 48tracks per song) down to two 4.7GB DVD's.
I now have the artist buy two 120 (110 after drivers)firewire drives that I use as master & safety drives. This lets me keep my four scuzzi drives as my "chalk boards". I also periodically back up keeper stuff to DVD. Then as then end thety got (at least) their two HD's and DVD's (I usually make mtself a DVD "just in case" copy for myself).