no path calculated in each frame, only when units step into a new tile, or when an unexpected and unresolved collision happens.
and paths very short for 80% of soldiers, depending on formation, they follow their fellows in the previous line, normally in 2 tile distance.
only the first line units, the leaders, make a bit longer path searches, about 20 tile distance.
and each search is cycle limited too, in case or errors.
so only a minor part of the full high level path is processed by units as tile level searches.