It's interesting to see what the actual stop times were, and time lost on the road, compared to what I thought they were based on memory. I can only really account for 10 minutes of that extra 30 minutes that I lost on the road.
If you're going to do a detailed plan with that spreadsheet (I'm not, I'm just getting a rough idea of various plans) then you want the information that goes in to be realistic rather than estimates based on rose-tinted memories of a ride.