It would be better if the searching of buildings wasn't random. I got through 3 towns and found very little of use. A couple of machine guns was as good as the weapons got, and most of my searches produced absolutely nothing - Not even supplies.
Took me 26 days to get the '6000 feets' achievement. Got it on the day that I had fully upgraded everything. I've read that people can get it even before they're fully upgraded, but the maximum I got before being fully upgraded was around 4500 feet. Come to think of it, I probably could have shaved a few days off my final score if I hadn't hung around to get the rest of the petty achievements.
 "The Last Stand 2"){kind=icon}
 "Learn to Fly"){kind=icon}