Dec 5 - increase mileage? speed?

Dec 5 – I’m doing 12 miles/day comfortably now.  I’m looking ahead to the Great Plains on the map, and seeing such vast distances between towns.  If I’ m able to do 13 miles/day across Saskatchewan, I could reduce the number of days I spend there.  But I remember how difficult it was to increase to 12 miles/day.  I don’t want to set a target that’s too difficult to sustain.  So, while I’m still “in” Alberta, I will try to increase my speed, and then see if I’m ready to increase my cycling stints at the provincial border.