If your talking about removing a top, it is best to this with at least a week, preferably two, still left in veg. This gives the hormones, called auxins I think, time to redistribute. As far as bending, I will pinch and bend my buds through the first month or so of flower as I sometimes need to keep them from getting too close to the light. I don't bend anymore than I need to and it dosent effect the yield. If you are bending to supercrop (increase yield), I think that needs to be done while in veg or very early flower.