The auto-save feature can also help in some of these cases (although remember me is the easiest answer). It your latest typing was 'auto-saved' then if you go the the same forum and 'reply to thread' just as you did originally, then you simply need to click the 'go advanced' button at the bottom of the blank reply you're about to post. One of the advanced options is to restore an 'auto-saved' reply. Might save some time if the auto-save captured your typing in the not too distant past.
Using 'remember me' is much easier unless you're in a non-familiar environment.