How about a different approach, of setting the index unusable, "alter session set skip_unusable_indexes=true", load, then rebuild the indexes? I find it more robust myself, as changes to index properties (tablespace etc) do not have to be stored outside of the existing index definition.

Are you using direct-path loads, by the way? If so, have you evaluated loading with enabled indexes in place? If not, I would strongly advise that you use direct and not conventional-path inserts