gilpin,
How long are you online before you are "logged out"? I have to say I have been logged in for hours and never got "timed out". So, I am not sure if it is a problem on the FT side or your own network side.
I also know people in the past have talked about how they accidently leave a public terminal and forget to sign out... so having FT do a sign out is good for them.
For example, I was in the LHR RCC last November and happen to come to the Flyertalk site. It took me there... but it automatically had me logged in as another user. I immediately emailed that user to tell him about the problem... and then logged him out.
Trying to be helpful... if your post is honestly taking hours to put together you may want to compose it in a word processor and then copy it over when it is finished. I know people do that with long trip reports.
William