There is nothing wrong with Mapblast... we use it too. But I have tried 3 different sites and I am getting 3 different durations for our trip. One says 14 hours. One says 17 and one says 16. That is big difference especialy when you are travelling with 4 boys....
We are doing the AAA trip tix, but wont get it for several days. I was just looking for another site to confirm one of these.