To what move depth should you analyze a chess position I'm trying to learn a chess opening and using a chess engine (stockfish8) to analyze the position but I'm wondering what move depth should I set it to (e.g., 25, 30 35 half moves).
Generally, the only reason running a chess engine at less than maximum power are time constraints or if you want to give yourself a chance to win, though in the latter case I'd still prefer to play human players instead.

Regarding the use of a chess engine to analyze the position in an opening in order to learn a chess opening I am wondering how you are going to practically do this? I mean, the engine will give you only a certain sequence of moves which it considers best play for both sides. It will not teach you the ideas/plans behind an opening which is the most important part and something which you can rely on if your opponent for instance does not play the expected move. It will not teach you about subtleties, like move-order changes or any sidelines.

I am not saying a chess engine is completely useless for studying openings. You could use it for practice games in a specific opening or you could study a certain alternative move in an opening (but that would be at a stage where you already know the opening somewhat).

For studying a new opening I'd find much more useful than an engine:


any explanation of plans/ideas (this can be books, videos, or a coach/friend)
a database
following games of a Grandmaster who is playing the opening regularly (let them do the difficult analyzing part...)