While 43TB is a large database by any standard, you might benefit from looking through all of your table spaces and checking if you are using good storage methods. I.e. that you don't have 5 or 10 data files attached to a table space when 1 or 2 will do. That you don't have excessively large blocks sizes in table spaces where you have a lot of smaller tables, etc. The larger the database grows the more room there is for pruning. IMHO, small bites of 5-10 table spaces at a time would make more sense than larger changes.