They be a limit on the dungeon so let's say you can only do 3 per day at 60min each that 180min If the mobs don't give that much good SP it pointless to do if you got all the Gear you need from it. The best thing to do would still be leves or solo or if they fix the dam issue with mobs giving bad sp me killing a 10-20 level over and getting 100+sp is not a smart thing to do.