The lengths of service loops is a judgement call. I only added service loops to the wires where I had to move the instrument to make the connection like the EFIS. On those instruments where I had easy access to attach/remove the wires without moving the instrument I added enough wire to make a comfortable connection, but not a 'service loop' length.
Here is a photo of all of the harness connections as installed prior to connection. As you can see the rearward wires are longer because the screen has to be pulled out and laid face down for easy access to the connectors;
This is an image of all if the engine sensor wires coming into the GEA24. There is no service loop, however there is enough length to allow working on the connector itself (as I had to do since I connected all of the thermocouples reversed) without much drama.
