I was actually more referencing what has been done in Laffer's name rather than what he actually said. His actual theory (which I understand) remains untested. Hardly any country has ever actually been at the peak of the Laffer curve but even if one had been - none has ever actually done what he actually proposed. Cutting taxes was NOT what Laffer proposed. Cutting taxes only on the rich was REALLY not what he proposed.
Laffer proposed a tax cut for EVERYBODY with short term spending cuts that match the tax cuts. Cutting on only the rich does NOT stimulate economic growth at all - they are already rich, you get MORE done by cutting on the middle class and poor and possibly enabling some wannabe entrepeneurs to afford to start a business.  
Not cutting spending means the whole plan falls appart.
Making the cuts permanent destroys it all - because it's harms outweigh any gains you can make. The cuts MUST be written in law to be temporary - ONLY until revenues recover.