Your guess is as good as mine what led to the somewhat longer than average time to get fingerprint and EAD. I see another case where the applicant has a very similar priority date to mine (within 2 days), did not use Premium for the I-140, still does not have the I-140 approved, and was fingerprinted a month before me. My guess would be that it's based somewhat on the demand at the fingerprinting offices local to each of us.