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I have long been playing games in which I can develop my bishop to g5 like in the following positions:
The truth is I have trouble deciding if such moves are useful. In the diagrams, what pushed me to playing such move is specially my pawns on e5. But maybe come to think of it, that is not much of a compelling factor. Is there anyway to reliably determine when this move would be worth it?
One-move threats are usually not the most productive moves to make. There are, of course, many exceptions to this rule. These exceptions should answer your question.
The attacked piece is on a very strong square (or has to escape to a very weak square). In this case, the black queen is on a kind of "meh" square - it's fine where it is for now, and it'll still be fine if it has to evacuate that square.
Setting up a pin. If black's only recourse in this situation was to put the knight in between the bishop and the queen, then a pin would be set up. However, there are other options for black to take, so this isn't the case.
(related to 1) Removing a defender - occasionally, one-move threats can force the attacked piece to stop defending another attacked piece. This is not the case here.
Messing up the opponent's pawn structure. If black's only recourse here was to play f6, it would be nice to bring out their f-pawn so early. However, black has other options.
Trapping the attacked piece (self-explanatory).
Developing your pieces. In this case, the attack isn't even the main point - it's developing your pieces that's the point. This happens regularly in the early opening of a game.
Consequently, if a one-move threat doesn't accomplish one of the above things, I would generally advise not making it. Of course, there are always exceptions to the exceptions to the rule.
When your pawns are on the dark squares, as in your examples, it is often "Positionally" desirable to exchange your dark squared Bishop so responses like ...Be7? would leave Black weak on the dark squares.
But in chess you must be concrete, which means you must calculate. What if Black plays ...f6 which is often a thematic assault on your pawn chain -- now with tempo.
Look over grandmaster games and learn from what they do.
