The sizes of lands ended up being quite consistent. All references to the size of lands indicate they are no larger than the distance a person can travel in two days. This includes major lands like Zarahemla. The size of each "land" is roughly about the same size. The only lands that are significantly different from this size are the land Bountiful, the land northward, and the land southward.

Livestock, at most, can travel 11 to 13 miles a day without adverse health affects. This applies to cattle as well as smaller animals such as goats and sheep. Early counties in the U.S. were determined by the distance a horse could travel in one day, or about 40 miles. Early Mayan polities (i.e. lands) were 20 to 40 miles across. [1]

A fair assumption is that the size of the lands were probably not larger than 30-40 miles across and not smaller than 20 miles across.

Notes:
1. Matthews, Peter. Late Classic Maya Site Interaction. A paper presented at "Maya Art and Civilization: The New Dynamics," a symposium sponsored by the Kimbell Art Museum, Fort Worth, May 1986. Polity sizes are reproduced in "A Forest of Kings," Linda Schele and David Freidel, William Morrow and Company, Inc., 1990. ISBN 0-688-11204-8