After much trial and error I've come to a rough timetable of waiting thirty or forty minutes and then checking the weight on the canner. If it is relatively cool to the touch, I lift it partway and if the steam just goes "psst" and stops, I consider that as reduced to zero. If the steam hisses out hard and fast when I move the weight, I leave it in place and try again later. Once the pressure is zeroed, I remove the lid and then wait ten minutes before taking out the jars. The most disconcerting thing is that I'm not hearing the jars "ping". All these years of doing water-bath canning, my favorite part is always hearing the jar lids "ping" and seal as they cool. I have checked the lids carefully and they seem to be sealed; I'm assuming that they're sealing in the canner as it cools and I can't hear the "pings".