Daily Quests are repeatable up to a total (for all Daily Quests) of 10 times per day. The count can be reset to zero by purchasing and using a Daily Quest Ticket from the Item Shop (for 39 ($1.16)† ) or from any Phirius Merchant (for 780 ).
An excellent hunting spot for these quests is a short distance from the water, amidst the bones at 51, 78. This spot is safe so you can rest here between fights, and both mobs you need to hunt (Mutant Seaweed Mud and Mutant Bigshell Crab) are in easy striking distance.