It is said that length matters. It is also said that length doesn’t matter. In the case of an I2C buss, the cumulative buss capacitance is what really matters, and that goes up with buss length. I was reading the I2C buss spec and getting nervous about it, so I decided to do an acid test. I had 6 feet of 16-conductor 3M ribbon cable, so I split it, put IDC headers on it, coupled them, then added the 3+ foot leg buss I already constructed.
All told this is 14′ 8″. At the rated 15pF/ft, that means for this buss the total capacitance is about 220 pF. Apparently that’s not a problem, and that’s a big relief.