The longest any of my packs balance is for a few seconds during the charge. If you have to let you pack balance for that long, one (or more) or the cells are damaged and is not taking as much of a charge as the rest of the cells. Passive balancing discharges at a very low rate, so it takes a long time to balance cells. The more out of balance the cells are, the longer it takes. You should use a DMM and measure the voltage of the individual cells as soon as the charging process is complete to see just how out of balance the cells are.