While I am not an expert in this area, I do have opinions, and they go in two directions. One is that I think it is important for each person to give himself enough time to satisfy his own sense that he tried for long enough--for some people it could be a year, for others it could be five years or longer. But whatever that amount of time is, and it might be stated out loud, when it is over and one has not had his career take off in the way he had hoped, then he can feel he has tried his best and then can move on to another (perhaps former or perhaps different) life. The sense of personally really trying though should not be cut short. And the time when it runs out for the experiment should be acknowledged.