Roughly how much time do you (GMs) spend prepping your sessions? Per hour, let's say. Obviously this will vary massively, depending on what the session contains, but I'm just interested in a rough estimate - I think I'm probably over-prepping, and I'm curious to see how my prep-time compares to other peoples.
As a bonus question, what do you find the most useful thing to focus on when prepping is? (And, by extension, what do you spend less time prepping?)
Thanks in advance.