One shot is one shot, In some cases in a pinch with some developers folks can run a second roll by developing for a longer time, as long as the second roll is developed within a few moments of the first one. (as one shot developers will not keep after mixing to working strength in most cases)

Best idea is to only use them one shot, and accept that you are throwing away some left over power. That is the Buffer than ensures that you have enough power to accomplish your mission.