Notwithstanding the claims of some DW appliance vendors that you just “wheel it in and slap your data on (just load, and don’t worry where it is) and then you do the analytics” a lot of organisations go along the long-established route of regular batch data loads to a data warehouse. These traditional data warehouses often have long life spans, they run day in day out for many years; and in my opinion to do that you need sustainable, supportable ETL code.
via Rittman Mead Consulting » Blog Archive » Simple Steps to Sustainable ETL.