play back rosbags

Hi all,

I’m trying to understand how ppl use rosbags for testing today, would really appreciate if you can share some insights:

What are the typically useful test cases when playing a rosbag back against ROS nodes? Like testing perception or path planning?
How long do these tests typically last? like a few minutes or hours?
How many of these play backs do you run concurrently? I can see a case where there are different input bags for testing a particular function.
Do you typically use tools like rviz or command line to inspect the topics when the play back happens?
Other than playing back rosbags against ROS nodes, what are the other tools you use to analyze the recorded bags?