People get different advice about this from their doctors (and sometimes get no advice at all). The advice I got was to gradually (and gently) begin to delay bathroom trips to “stretch the pouch.” For most of us the delay is mildly uncomfortable - agony or accidents are not a normal part of this process. So what happens if you don’t obey the signal you’re currently using as your cue to go to the bathroom?
Formed stool isn’t optimal for most J-pouchers. Some do just fine with it, but for many it can be a sign of not drinking enough water, and it can cause straining on the toilet, which leads to other problems.