When did having an Exchange Admin account become obsolete?

I am having a dispute within my company.  At one time (up through Exchange 2003 at least, I believe) it was necessary to have an Exchange Admin account (with the Exchange Full Administrator role) to perform certain tasks even for a small or medium business.  For example, when performing an Exchange migration from one server to another you might want to export mailboxes databases to PST files for later import back into a new Exchange server.  I believe there were other functions also where an Exchange Administrator or Full Administrator account were necessary even in a small  business and where a Domain Administrator account was insufficient.   (It may be true that in larger organizations Exchange Administrators are still necessary due to separation of duties on an IT staff.  But in a small business without any IT staff this is unlikely to be the case.)

I have been told that "at some point" in the past this ceased to be true and that Exchange Administrator accounts were no longer needed for such purposes (like Exchange migrations) because Microsoft made other tools available.   Therefore, the logic goes, we should delete or disable any Exchange Administrator accounts we or our small business clients still have in existence as they are not needed.

My question is if Exchange Administrator accounts are no longer routinely needed when EXACTLY did this become the case?  Did it happen when Exchange 2007 was introduced?  Or maybe Exchange 2010?  Or maybe at some other time when Microsoft introduced some additional tools to facilitate migrations?

Ideally I would like to be able to point to an official Microsoft publication (TechNet, blog article, whatever) as proof of the timeframe when Exchange Administrator accounts became not typically needed.

I am looking forward to some gurus being able to answer this question!