You will only need the two lines at the beginning of the page, no matter how many editable areas you create. These are the includes that point to the files the page needs to call (refer to).
The 'Page Name' should be the same for all the edit areas in one page, the 'content areas' need to be uniguely (and descriptively) named though.
5 instances of the "body placement" code,
Two lines only (one pair) of includes.
I don't think there is a theoretical limit to the number of editable areas (but probably a logistical one)!