Well, in terms of clearing/uncovering the map an hour was about the average. Give or take as I already said above. If one wanted to find all the nooks & crannies, I reckon that will take longer. But I specifically mentioned that as well.@Fencers: oh you meant a single map... well by rushing through you could get this in one hour. Is this actually fun for you? Well some guys (and girls) like speedruns, can't argue with that.
Personally, I am not an explorer type. More of a task master-type player; setting up a specific, achievable and predefined goal(s). Though it's fun to backtrack after I got the map filled out. It'll drive me CRAZY to wander about without tackling an area systematically. ;D