There is never a need to "re test" a DNA test that has already been done. The science is exactly the same and there are never and "different" results, especially when a match has already been proven. If you do not understand this, then you do not understand how DNA testing works. DNA testing only gets MORE conclusive with advances, but that does not decrease the fact that a match has already been proven.
It is a waste of time and money to do another DNA test because nothing will ever be different.