Its great to have quads, because you are almost 100% sure to win the hand. But its actually not the most profitable hand to make, since you have so much board lock, its difficult for the opponent to have something, they can pay you with. On a board like JJ6 I would rather have 66 than JJ, because if I have 66, the opponent can have JX and put a lot of chips in with a second best hand.