Just a couple of points to consider.

I think a lot of people would be surprised at how far they can walk in a day if they had to, but even more surprised at how short of a distance they can cover in a week.
here is some discussion of Naismith's Rule for estimating time to hike a distance
Here is another thread on it at Backpacking light forum

Notice that Naismith estimated 3 miles per hour on level ground.

On a prepared road you might cover 30 miles in a 12 hour day (4 half hour lunch breaks), but if you are out of shape and carrying a pack it will likely drop to less than 20 miles. Possibly as few as 10 miles.
The likelihood of going more than thirty miles a day for more than three days is very small.
If you look up some of the famous forced marches you see they were usually pretty slow.
You might find the story of General "Vinegar Joe" Stilman's retreat from China into India interesting.
It took them 16 days to go 150 miles and they drove at least 50 (possibly 70) of those miles over 4 days.
That left at most 100 miles walked in 12 days.
Less than 10 miles a day by a group of young, fit men with the Japanese army chasing them.
Lacking the incentive of a bunch of armed men behind you and being less fit 5 miles a day is a more likely rate of travel over a long distance, especially if the route is rough at all.