Spouse's Best Age to Apply for Spousal Benefit

Mine is a simple question: I will turn 66 (my full retirement age) in April of 2012. I plan to hold off on applying for my SS benefits until I turn 70 (I plan to stay fully employed at least that long). My wife also turns 66 in October of 2012. I want to "File and Suspend" in 2012, which I understand will allow my wife to file for her spousal benefits (based on my earnings). Is there a benefit advantage for her to wait until she turns 66, or will my being 66 provide the same level of spousal benefit? In other words, will she get the same benefit from filing for her spousal benefit when I turn 66, or should she wait until she turns 66? It seems to me, that since it's my earnings that determine her spousal benefit, she should go ahead and file for them when I turn 66.
Any advice will be appreciated.