Hi,
A good (Enterprise) Data Warehousing / LSA (Layered Scalable Architecture) principle is extracting the data once and storing it in source system format in the Corporate Memory layer (long term, all extracted data, all fields), next to the Propagation layer. Purpose behind it is that you are not dependent on your source system anymore for historic data. E.g. in case archiving takes place.
Extraction from an archive is optionally available and DataSource dependent. So you cannot rely on that. Please make sure to extract the data once only and to store it in the Corporate Memory so that you do not have to extract the same historic data anymore in the future.
Best regards,
Sander