Not sure why you'd run out of time, as the "time-out" period is one hour.
However, if you did sit for any hour when typing a post without doing anything else, then yes ... you would be timed out and lose your connection to the site.
When I create a post of any substantial length, I simply type it up in my text editor and then cut-n-paste it into the post when I'm ready to send it ...
Regards,
Doug