Mr Light wrote:
Most comic books only take place over 1-2 days. And each comic ends on a cliffhanger that leads right into the next. So 700 issues of Superman would only equal 1,400 days, or 3.8 years.
And then you count time between story lines. Normally five years of real time is considered one year of comic time. Marvel seems to reference this every once in a while, and there was supposed to have only been a little over two years between Superman's death and Infinite Crisis I think.