In Canada, four to eight weeks is the length of time between calling an election and holding it. The 2006 campaign was a long one, lasting eight weeks, because of the year-end holidays.

In the States, they do drag on. And on. And on.......
The period was set before highways and fast communications tied the country together.
However, they do allow time for people to think, but in the current campaign it is becoming obvious that Obama has little to offer, and McCain isn't the brightest light on the tree; Congress will continue to be divided on approaches as it has for the past eight or so years and will continue to muddle along without much accomplished.