We rarely fail to get a 40 unit bag in a 35bu box and usually can get 45.  With our small fields, filling up, and moving a 100 acre day is still considered good to us and we can generally beat it.  Get on the right farm and 80 feels like an accomplishment some days.  150 would be possible in corn but rare as I tend to get off at least once an hour to look things over and dig.