How many uses does a Microsoft Office 2010 Professional Plus key get?

An MS Key does not run out of uses, a retail MS version can be installed/activated as often as needed, provided its no on more working PC's than the licence allows for, allthough you may have to use phone activation and not respond to the auto prompts untill given the option to speak to a real person

Office Pro Plus for $300 is not a realistic price from MS. The list price for Office Pro Product Key card is $350, I could maybe see Office Pro PKC from MS on sale for $300.  But a PKC license only allows install on one machine PERIOD, no transfers. 

The only other possibility that comes to mind is a Technet or MSDN subscription. They used to allow 5 or more installs, but I don't think they were that cheap, and they are an annual subscription payment required.

That is what I must have because I have it on over 5 PC's.

You can activate it concurrently on two PCs. It is transferable but you will probably have to activate by phone.

Hi Kenny,

Thank you for posting in Microsoft Community.

You may refer to the Microsoft License Terms in the following link and check if it helps:

http://office.microsoft.com/en-us/microsoft-software-license-terms-for-microsoft-office-2010-HA101817777.aspx

Hope the information is helpful.

Thank you.