Preserve input sequence length now by default

src/exdf/cli/reduce.py

@@ -98,9 +98,9 @@ def _parse_args(argv):
 
     output_group.add_argument(
         '--output-sequence-len', metavar='NUM_TRAINS', action='store',
-        type=int, default=500,
+        type=int, default=-1,
         help='number of trains per sequence file or non-positive value to '
-             'preserve input length, only used for `collection` and '
+             'preserve input length (default), only used for `collection` and '
              '`collapsed` output layout')
 
     output_group.add_argument(