> I have learnt to copy to an editor before I post if I took a long
> time composing the response.
Me too, but the longer I do that, the more complacent I become, until finally I forget there's a problem and I lose a post.
> There must be a session timer on the forum, so it would be good if the
> post pages had a timer and disabled the buttons when it expired, which
> would stop the loss of typed text.
> A countdown label would be good as well.
I'm not sure if the post is doomed from the moment you start typing it, or if it times out if you take too long typing it. If it's the latter then we can't expect the buttons to change between rendering and clicking. The countdown is a good idea.
A warning on the submit button might be a simple workaround.