For me...it just depends on what my goal for the day is, and how much time on the water I have. If I'm just out fishing with a friend or two for a 1/2 day, I'll probably fish known stuff 80% of the time. If I'm fishing by myself all day, then I'll prob only fish old stuff 40-50% of the time.
Another example...I have been spending time on smaller lakes across East Texas this Summer/Fall...many of them I have never been on. My goal for each of these days has been to graph 80% of the lake and mark what I can find...then go back and fish whatever I have found for the last 20% of the day. Then the 2nd time I went back to that lake, I reversed it and fished things I marked 80% of the time, and spent the last 20% of the day graphing the part of the lake I did not cover the first trip out.
For me, it's not always about today's trip to a certain body of water...it's more about the next trip