The distance limitation is because in a parallel data cable, seperate bits of data travel down different wires in the cable at the same time.
The trouble is that due to natural variation, data travels down some of these wires a little faster than others. Over a short distance, this doesn't matter, but over a long distance it's enough to cause "data-skew", where the data doesn't arrive at the same time, and this causes corruption.
It stands to reason, however, that your parnet cable can be as long as any printer lead. The longest printer cable I've seen was probably about 5 metres. (Edit: I've just seen a 10m cable for sale online. Couldn't find anything longer than that.)
