Daishain’s 5e D&D Rules, Q&A, And Support RPGs PBP Pathfinder / D&D The Sage says...
No problem Kyr.
To calibrate you guys on distances covered, heavily loaded wagons typically make only 10-15 miles in a day, with 20 being doable but risky. No, that doesn't quite mean that they're only going 2 MPH while on the move, but rather that much of the day is dedicated to rest.
A lone horseman can go much further, as much as 100 miles in a day if the rider is light and the horse has excellent physical training, but without a remount will they be forced to stop for at least a day after such a feat. Your group is working with relatively light wagons, and have a large number of spare horses on hand, hence able to maintain a pace that is actually quite a bit faster than the norm. Really makes you appreciate modern automobiles eh?