Prep soil -> Plant -> Wait -> Harvest
Perennial grains would allow you to do the prep and plant once, and then repeat the last two steps multiple times. Prep, Planting, and Harvest are all similar orders of magnitude of labor, so if you can get ~ 5 years from a single planting, you could work an area of land with less than half the total labor.
Less soil prep and planting (with heavy machinery) means less soil erosion, less microbiome destruction, healthier soil.