6 Miles!!!! I have ridden from Melbourne City to Home a few times - Distance 43 odd kilometers.
And these were always drunk - I would drink, miss the last train home, and then have to ride. Takes about 1 hour 45 mins (on lowriders/Krates), but I have never done it on a bike with gears or good riding position ie: MTB or Roadie.
I did get a flat once, walked half way home before finding a servo with a puncture kit, then another 5 km to another servo with a working tyre pump.
Always fun.