STRETCHING OUT

Fires when today's distance exceeds the maximum distance in the last 10 valid starts by more than 220 yards. Unlike SPRINT_TO_ROUTE (which flags a specific type of distance change), STRETCHING_OUT identifies an absolute distance extreme — the horse is venturing into completely unknown territory. Stamina is at least partially genetic and develops with racing experience; a horse facing its longest-ever distance may simply not have the physical resources to sustain speed for the full trip.