It will depend on the grain you are milling e.g. red spring wheat vs super hard durum, the fineness you’re targeting for the flour, and to some extent the ambient temperature.
I’ve never tested this but have read that the Mockmill 100 can mill 5kg flour before it needs to cool down for awhile. At 100g per minute, that is 50 minutes of milling.
Edited to add: Try 10 minute sessions on fine grind, for the 100 series = 1Kg = 2.2 Lbs and for the 200 series = 2Kg = 4.4 Lbs
I usually mill 500-900 grams at a time. If I were trying to get many kilos of flour per day, I guess I would space out the milling sessions and maybe freeze the grains.