It's been suggested that renumbering is a fact of life; everyone will
do it at least once in their lifetime. This is one of the reasons why
an entire working group in the IETF has been created to deal with this
from an operational perspective. See:
http://www.ietf.org/html.charters/pier-charter.html
and
http://www.isi.edu:80/div7/pier/
See also RFC2071.
- paul