Sorry, I don't see the problem.
It is obviously better to land in a field with some fuel on board than run out and be in a dead-stick situation. There therefore has to be a time when you are going to have to make the decision that you are not going to make your destination. It is a command decision where that is, and of course landing at an airfield with 25mins fuel on board is safer than landing in a paddock with 30- but how far are you going to push it?
Now, the piece I really can't see is why WOULDN'T you declare an emergency? Being at the point where fuel exhaustion is a possibility is obviously an urgent situation, and the idea that you'd keep quiet is irresponsible.