Here is what we do...

1- Export affected partition (exp/compress on the fly)
2- Move dump file to tape
3- Drop affected partition
4- Coalesce tablespace

Notes:

#1 For some tables where we know reload is likely, we do not drop the partition, we just truncate it.

#2 Since all our indexes are partitioned, no need to rebuild.

#3 Since we do not have a tablespace per each partition, no need to deal with empty tablespace.

By the way, we move selected Data Warehouse data to tape after seven -as in 7- years.