We make the decision on when too sell and whether to wean or sell off the cow based on pasture availability for them. As to days of weaning. It used to be the barns here wanted 30 days, then 45, then 60 and now some say 90. Have talked to barb owners, feedlot buyers and managers and my vets. The vets say after 30 days any effects of weaning are over and it is post weaning management and conditions that play into it. Have been told by some that increasing the days weaned is one way of increasing the age on the calves. We have had mixed results weaning them, we have made money doing it then like last fall the feeder price dropped enough we didn't make anything weaning for 45 days. We sold some 850 wt 100 day weaned steers this week. If we had kept them on the wheat another 2-3 weeks they would of made more. But we needed to pull bulls and a place for them. We have too consider what works best for our whole operation. We have several bulls we used as yearlings last year we want too run on wheat for 45-60 days. Again we make all decisions on calves and whether to wean or not based on current conditions. If we wean we usually wean for at least 21 days after that it depends on feed availability.