I am a beginner swimmer. I have found for me that my first two laps I can do every three, but eventually I have to settle in to breathing every two strokes. Then as I get 'in a groove' I can sometimes do every three once per lap or so.
Or sometimes I settle into a breathing pattern of 3-2-3-2...And that works most of the time.
Occasionally I will be off in balance and get a mouthful of water, and that gets me a bit panicky, so then I have to go back to breathing every 2 for a while. Until I settle back down!