Howard states:
[ ... ]
IMHO, I don't think you can guarantee that almost anything will stay
routable, certainly anything less than an /18. Bluntly, there's no good
way to guarantee routable prefixes.
Yes, there is a good way to GUARANTEE routable prefixes. Intermediate
system address translation which maps to "virtual renumbering"....
The answer my friend.... is blowing in the wind... in the technical
implementation, not "human attitude re-engineering".....
The attitude, .... "bluntly, there's no good way for man to fly...."
is not unique to written history.... it is alive and well in the
Internet today 
Best Regards,
Tim