I am not sure when I should ask for perspective.
As often as you can. The coach cannot give you perspectives on many things simply because giving perspectives without context has little impact. So as the coachee, if you ask questions based on the problems you are facing, the coach can give correct perspectives that you can use immediately.
It requires you to be aware of the situations, to know where there are potential areas of problems, to be able to put principles into practice and identify areas where you were unsure or got stuck. When you keep asking from that perspective, the coach can really enrich your experience by adding his perspective.
Many times, this may only require a couple of minutes - hey coach, I am doing this. Is that ok? And coach will say, I think this is what the principle is, and you can do it this way, but keep this in mind while doing it.
It really helps. The smartest coachees fully take advantage of the coach that way.