I have 20' guitar cord and a 25' headphone extension cord that I combined into a "harness" by using some heat-shrink tubing rings every couple of feet.
I made sure that at the end I plug into the guitar...the headphone extension jack ended up just a bit below the guitar plug, that way when I plug in the headphones, the plug can go in without jamming up against the guitar.
I also have headphones (Fostex) with detachable cables. So I remove the stock cable which is like 12' long, and I made a couple of short, 4' cables for the headphones when using them with my guitar. That way, there is only just enough headphone cable to reach behind the guitar and plug into the harness...and I don't have a pile of cable hanging.
I guess you can also just fold up the excess headphone cable and use a Velcro tie if you don't have detachable cables.
Anyway...when I'm tracking guitar, the headphone extension cable and guitar cable move as one, with no excess headphone cable hanging down by my feet and getting in the way. I can move about freely and I don't get all tangled up between two sets of cables.