as others have said, this seems to me to be a logical confusion between the physical layer and the symbolic/representational layer of control.
the intellectual description is not, and should not be in the design of our discovery and access tools, actually tied to the physical--if a collection is considered an organic whole, it should be described as a whole.
It could then be physically stored and physically accessed in 1 place, 3 or 500 places, or on a hard drive. The intellectual layer would be unchanging in that case, and also in the case where the collection is moved to a different storage location (or hard drive array).
I am curious, though, about how various institutions handle ongoing accruals. We have some collections where we receive periodic donations, but at irregular times. These are still considered part of the original collection. I would think that an entry into the <accruals> tag or parallel field in a database, would be sufficient.
Laurie Lee Moses
Archivist & Digital
Center for Black Music
600 S. Michigan