This Saturday evening we're going to be replacing our existing Windows Server 2003 domain controllers/dns servers with Windows Server 2008 R2 domain controllers/dns servers. The current forest and domain functional levels are Windows Server 2003 and I've already run adprep /forestprep and adprep /domainprep /gprep from the W2K8R2 media on the existing schema operations master. I've also installed the AD DS bits on the new servers but haven't run DCPROMO yet. Our AD DNS zones are AD integrated.
Is there any reason not to go a step further and "pre-stage" the new servers by running DCPROMO now? We won't be cutting over to them until this Saturday evening but I don't see any harm in getting as close as possible in our preparations before then.