Let's say someone has four CAT5 cables that are running along the ceiling for the length of a room (30 feet), of which most of the twisted pairs are connected to Arduino input/output pins on one end. Would it be okay to keep these wires bundled together when running along the ceiling? Or is it safer to keep them separated by a few inches? Is interference usually a problem only in very specific situations, or should it be considered for all long wire runs?

How about if there is a telephone cable (hooked up to a landline telephone) running along the same length? Is there any chance of interference if this is too close to the Arduino cables?

How about if there are 120v mains lines running the same length? Should these be kept at a distance from the Arduino cables?

On the other end of the cables that are hooked up to the Arduino, some of the following are connected: temperature sensors, light sensors, servo motors, LCDs, relays, and push-buttons.