I actually think that is a great method. There isn't really a standard for time for fermentation, it is dependent on temp, pitching rate, wort make up etc. Personally I give ales a week and then check gravity against the expected anneuation for the yeast type. For a lager I'd go two weeks and do the same.
One potential improvement would be to get a refractometer to conserve the beer instead of pulling enough for a hydro sample.
Experience is the best chart you can have for fermentation. But that's one man's opinion.