Use mkvtoolnix to split video file such that each file in same duration?

This can be done quite easily with mkvmerge using a simple variation of the --split option:

mkvmerge --split duration:00:10:00.000 input_file.mkv -o split.mkv

This unadorned command line (other much more complex options are available for --split) will produce an out file naming pattern of split-001.mkv, split-002.mkv, split-003.mkv etc.

The full man page entry for time / duration splitting with mkvmerge is as follows:

2. Splitting after a duration.

  Syntax: --split [duration:]HH:MM:SS.nnnnnnnnn|ds
  Examples: --split duration:00:60:00.000 or --split 3600s

  The parameter must either have the form HH:MM:SS.nnnnnnnnn for
  specifying the duration in up to nano-second precision or be a
  number d followed by the letter 's' for the duration in
  seconds.  HH is the number of hours, MM the number of minutes,
  SS the number of seconds and nnnnnnnnn the number of
  nanoseconds. Both the number of hours and the number of
  nanoseconds can be omitted. There can be up to nine digits
  after the decimal point. After the duration of the contents in
  the current output has reached this limit a new output file
  will be started.

How cool is the command line :)