Look on Microsoft's Support Life Cycle page gives you a fuller picture.

I use Office 2000 on a machine at home which is still merrily working 5 years after all support ended (and have a friend using Office 97 which went out of support 12 years ago) and it still works fine.

I'd reckon that it is more likely that something mechanical on your machine will fail before the extended support for Windows 7 (which is mostly about security rather than needed functionality)