It isn't realistic to expect a profit on ALL your overlays, because by wagering in such a manner, you might be betting on half of the horses in the race. Showing a 10% profit on your top pick after 352 races is unquestionably a GREAT handicapping exhibition.
Those who say that watching replays is "a must in order to win" probably need a new set of speed and pace figures...along with some improvement to their figure-interpreting skills.