To make the actual window longer, you would just punch one window, then move the punch toward the end of the window you just punched and overlap the ends of the punched windows to keep the edges of the finished window even. Clear as mud?
punch --> slide to overlap rounded ends and make window the length you want, line up to be sure edges are straight --> punch again
Check out this thread:
Word Window Wow Workshop for lots of ideas.
HTH!