I've never flown in complete darkness but have used RTH to land my drone in twilight conditions long after sunset. No need to adjust RTH altitude if it's already set to clear local obstructions. Trees and powerlines don't get higher at night...
Situation: A dangerous dead branch sitting on another about 30 ft up above a driveway which constitute a huge hazard.
A ladder was out of the question even if one that long was available. Consequently, I used the DJI NEO to carry a fishing line...
Little Neo for the win.
We use it at work for public safety. Since we already have an Avata 2 for entering buildings, we use the Neo for times where we may lose the drone such as entering a building post fire to assess for structural soundness...