http://www.vacmotorsports.com/faqsDetail.php?catID=10
Q: Can I reuse an MLS gasket?
A: Here is our take on this.
If the engine hasn't been run very long (less than a few hundred miles or less than a few hours) an MLS gasket can almost surely be re-used if you have to remove the head.We go by that guide and haven't had problems. Some people get away with a longer period, but due to the fact everyone has a different project and variance in between, there is no standard suggestion.
One thing we can say, is that
if the "black coating" layer on the top and bottom of the gasket has come off in any way during removal, it should be discarded and replaced.
I completely agree with the above tuner. This is how I do it.