Received the HV-H91DJ on Friday. Initial impressions had me a little dissappointed as the mids were pretty blanketed. But after about 10 hours burn in they got SOO MUCH BETTER. Planning on burning in about 20 hours total before beginning the review process. So far impressed for the lower cost that they are as good as they are. I'll keep you posted.
Burn in for more than that. I recently got the V-Moda XS and they took 36 hours with pink, white, and brown noise burn-in.