I stumbled across this really extensive look at camping, vision and attention levels, and standing watch.
A Sharp Lookout: How Much Can You Adventure?
By Mike Bourke
For a GURPS DF game, this isn't strictly necessary; GURPS handles much of this natively (light levels and night vision, time spent moving vs. camping, camp requirements, etc.) especially given Dungeon Fantasy 16: Wilderness Adventures. That said, it's still a fascinating read and has some value for GURPS. I found it interesting that night vision starts to "kick in" at 10 minutes, and may take hours to really peak. Also the incidences of hallucinations and "seeing things" that occur in low-light watch situations and long-time gazing at a single place. There is a also a useful discussion of alarm trips with bells, although in GURPS a simple Watchdog spell can solve much of the problem that actual guards are meant to address.
From a pure real-life education standard there is a lot there. It's worth it alone for the discussion of 90-minute sleep cycles, something that gets talked up in the sports performance field a lot these days. Or at least the corners of it I hang out in.
It's a long read but a good one.