FR: multiple scheduling of one item?

[Adam Spiers <orgmode@adamspiers.org>]

Imagine I have a single project or task which I know will require
several sessions to complete.  Before I get to the stage of analysing
it closely and breaking it down into sub-tasks, it would be good to
reserve some diary time in advance, so that I don't accidentally
accept other commitments for that time and overstretch myself.

However, this is different from booking a normal diary appointment, in
the sense that I am not making a commitment to other people to be in a
particular place at a particular time: the commitment is only to
myself and is directly associated with a particular project or task.

Therefore it sounds like it would be useful to be able to schedule the
same task for multiple slots.  It turns out that the org-agenda code
already handles this beautifully; if you do:

* Long task/project not yet broken down into sub-tasks
  SCHEDULED: <2008-01-07 Mon>
  SCHEDULED: <2008-01-08 Tue>

and it appears in both places in an agenda view, and you can jump back
to the item in the normal way.  The only downside is that C-c C-s
doesn't currently support entering it:

  (org-schedule &optional REMOVE)

  Insert the SCHEDULED: string with a timestamp to schedule a TODO item.
  With argument REMOVE, remove any scheduling date from the item.

How about doing the usual trick of comparing different prefix argument
values (e.g. 4 vs. 16) to allow adding a new scheduled slot?