Way to insert million records(8 crores) into table.

My problem is every month end i have to insert million of records (8 cr) records into the table containing 5 indexes , i have been using pl/sql program to do this process with the help of bulk fetch and bulk insert which it takes 5 hrs. so i want to the procedure which i can follow to finish this process as soon as possible.

Drop indexes (or make unusable), insert /*+ append */, rebuild indexes.

Building on Stecal answer - if issue is related to I/O contention you may want to consider hash partitioning on target table.