Some newsprint may last longer than others, but in general, newspapers turn yellow and become brittle after a fairly short period of time. That's why the US Constitution is stored in such an elaborate way, and why big libraries tend to have important and old papers/books stores in a secure vault, and keep newspaper archives on micro film. The Smithsonian has instructions on how to preserve newspaper, and reasons why it deteriorates so quickly: http://siarchives.si.edu/services/forums/collections-care-gu...

I saved some papers from 9/11 in a shoebox in a closet, and when I opened it 10 years later, some of the papers crumbled in my hands. Paper of any kind is fragile and easily damaged by humidity, weather, and fire. We give books and newspaper special treatment every day they're kept safe in our climate-controlled houses. If civilization came crashing down, these archives would be lost very quickly.