Will things get so tough that I will have to ask my customers
  to renumber because I need to switch from a clutter of small spaces
  (as built in slow start and and with allocations not larger then /16)
  into a larger single prefix space? - even when I started out with
  provider aggregatable space, and tell customers that address space
  cannot be moved to another provider and I'm warning them that using their
  old numbers we cannot guarantee "full" connectivety.


- if large scale renumbering needs to happen, the problem seems to be analog
  to memory allocation systems (on the fly); I faintly remember that
  this could mean another factor of ineffeciency for the use of space.
  How much will this reduce the expected life time of the IPv4 space?
  (well, of course, under exponential growth it will be not very much)

  Already proposed this model for managment of the IPv4 space.

BTW we would need to recognize the need for large scale renumbering a couple
of years ahead - else we will not have the tools to do it, not to think
about the need to educate network and systems administrators...

  Yup. See the latest draft from the IAB and