Break rosbag record's --split option into --split-duration and --split-size. This will make it clearer how --split* options related to the --duration and --size options and will allow them to work together in a use case like:

rosbag record --split-duration 2m --duration 10m topic1 topic2 topic3 -> Will record for a total of 10 minutes, but will split the bag files up by two minute intervals.

See: #2