No question is a bad question!
It is difficult to judge how long an answer interviewer expects. Interviewers also have differing spans of attention.
When you feel the urge to go on while answering, it is always a good idea to take a pause and ask the interviewer if they would like you to go into detail. You can also ask them if there is any specific part of the answer where they would like you to shed more light. A general rule of thumb could be to speak for 60 secs and then take a pause to calmly ask the interviewer for directions
You should also take the help of visual cues from the interviewer on whether they are attentively listening to you or distracted by looking around, reading, etc. If you feel that you are losing their interest, it is a good idea to take a pause.