Indeed. Assuming those are 60ma nodes, that is 3A at peak brightness. At 55 feet, one of your leads has a resistance of .56 ohms, and the other has a resistance of .28 ohms, for a total of .84 ohms. That equates to a voltage drop of 2.52 Volts, which is a bit beyond where I would be comfortable running 12V pixels, especially if they are in a linear configuration more than a few feet long. If they are 30ma pixels and the pixel string is not too long, then you're probably fine.

Just for comparison, if you were to make it 3 + 3, instead of 2 + 4, the voltage drop would be 2.24V. 'Not a huge difference, but something, especially if one is right on the edge.