Fucking christ... I just got lost in a mineshaft for almost two hours. I thought I couldn't possibly get lost in one since they were organized. This was my first time exploring one, so I really didn't know what to expect...
Didn't keep my torches lined up, just put them all over the place. Then... Yeah. Lost. Completely.
In the end I got out with 90 iron ore, 23 string (almost all from spiders I had to kill), 14 lapis lazuli, 14 gold ore, 6 iron ingots, and 6 diamonds.
But, as a friend said after I told him the story:
Yeah man, shit gets rough. Especially when you end up in one that leads to another. Also, cave spiders are pure terrible.