I you live an an area that gets cold, use a real back pack and not a bag so that you can carry a real sleeping bag and tent or tarp/mylar. Good luck out in freezing weather with a tube tent or space blanket! I have camped many nights in the snow and I have mostly done it with just a 9×9 mylar , tarp, and backpacking matris and sleeping bag. I think it would not be good at all with just a tube tent/space blanket that is on a lot of BOB lists.
The term "bug-out bag" is related to, and possibly derived from, the "bail-out bag" emergency kit many military aviators carry. In the United States, the term refers to the Korean War practice of the U.S. Army designating alternative defensive positions, in the event that the units had to retreat. They were directed to "bug out" when being overrun was imminent. The term has since been adopted by military training institutions around the world, with Standard Operating Procedures involving a bug out location, a method of withdrawal, and the bare supplies needed to withdraw quickly but still survive in the field. The concept passed into wide usage among other military and law enforcement personnel, though the "bail-out bag" is as likely to include emergency gear for going into an emergency situation as for escaping an emergency.
Some will think the omission of foodstuffs from this bug out bag to be a bit odd but it’s not if you think about it. It might be years before you have to use the bag so it makes sense that you’ll want to procure your own emergency rations and review their condition a couple of times a year, replacing anything that might look dodgy. That said this bug out bag does emergency kit right with the aforementioned items as well as a dozen pouches of purified water, rain ponchos, quality toothbrush and toothpaste, shaving razor, comb, emergency whistle, emergency blankets, survival handbook, duct tape (!), paracord and more. There’s also the obligatory deck of cards for when you finally settle into the emergency shelter. Toss in some dry clothes for everyone involved, charger cords for your smartphone in case you run into a power source and a good book or two and you’ll be ready to wait out events in good shape.