Archiving RAW Files

I am beginning to wonder about digital archiving practices, specifically when it comes to RAW file formats.

Currently, The New York Botanical Garden Herbarium archives RAW files (Canon's CR2) and a Production Master File (TIFF). Jpegs are derived from the Production Master file for access in the Virtual Herbarium.

I am not certain what role the TIFFs play and why we should be archiving them. They consume a lot of server space, and therefore cost a lot of money to store. Isn't the RAW format sufficient for the purpose of archiving?

The traditional belief I hear a lot is that since RAW formats are proprietary to the camera manufacturer they are subject to the whims of the market place and may not be supported in the future. Aren't all archives subject to technological change? There is currently a collection of 3000 35mm slides in a closet upstairs. A slide archive is not very much good without a slide viewer and hardly convenient or easily accessed by the public.

It is commonly believed that TIFF is a more broadly supported format and that the decoding of TIFFs is well documented. Of course, DNG, Adobe's RAW format could solve this problem. It is well documented and the instructions for decoding the files are readily available.

I guess, just like the slide collection, should the day come that RAW formats are no longer supported the images will have to be migrated to the next format.