I've been known to do this on maps I'll need in a hurry.

These days, mostly for budget reasons, I've been using my gutted deLorme atlas a lot. It's got enough that you can navagate by it, and it is generally only 5-10 years out of date. (Around here, the USGS maps have often gone 10-25 years without being photo checked. *shudders*) First thing I do is remove the in-town maps, and the touristy stuff. Keep that first page's map- that gives you the grid for your area and the key. Then stuff it in a freezer bag or two. For under 25 bucks, I get the whole state, rather than half the country- so it isn't accurate enough to call an airstrike and it lacks power lines and the like, for the money I'll take the difference.