Partitioning is mainly for incrementally loading data by say a date column. If the Monthly or quarterly data is new in terms of in the last month time stamped and no update to previously imported data, there is value.

File Groups are used to separate the files in the database on different LUNs (SAN) or hard drives. That would be your only benefit if you have separate drives or LUNs to place the files in file groups.

For performance, you might want to look into Indexing strategies. I have seen huge performance improvements on loading the data in a data warehouse where a fact table was completely rebuilt and we dropped the indexes first, truncated the table, loaded the data and added the indexes.

The table was mostly duplicated from an OLTP system, but the indexes on the OLTP where different than the fact table because the reporting and querying where different in the 2 systems.