sbs 2003 to 2008 migration - removing dc

Hi,

I am in the process of migrating sbs 2003 to sbs 2008 using the microsoft
procedure. The sbs 2008 is installed and up and running, having all FSMO's.
There is a 21 day grace period where both sbs can cooperate and we are at day
22 now because of a lot of reasons. So basically we have to migrate the
printers, files, infrastructure (dhcp, dns, etc...), exchange, etc...So now
the sbs 2003 shuts down every 2 hours because of eula (can't have 2 sbs on
the same network).

Here is my question; is it a good idea to do a dcpromo to remove AD from the
sbs 2003 now even though nothing has been moved. Meaning that after doing
this, exchange needs to continue running (I don't see a problem for other
things like infrastructure, file, print) until it has been moved. I am asking
because it means not following exactly the steps in the microsoft migration
process.

thanks