Longer does not mean that it will absorb all the flavours. Maximum for flavour absorbtion is only 2 hrs. The longer you marinate, the softer it is.
I usually marinate my beef in olive oil, lots of garlic, thyme, dried basil and a lil pinch of sugar. (1 piece of beef, 1 pinch of sugar. Sprinkle on both sides.)
Remember not to overcook it. Slightly undercook is the best. Overcook = rock hard meat xD