Are you doing a mileage run? Should be doable as in the new Airport, there are quite a large number of immigration counters so you are out in like 10 minutes. Note that it is a fairly long walk to the immigration counters, 10 minute walk at the very least, so be sure that you are one of the first ones to disembark. Check-in closes at 3:30 am sharp (1 hr prior to departure), so it would be good if you can get your BP printed at DXB itself so you don't have to worry if you get delayed a bit.