The main forum page can take a few minutes to update to the last post. Like with making edits to your profile, it can just take a short time to refresh and update the servers.
Sorry about this, but the delay should never be too long.
As for double posting, if the system is moving a bit slowly, no need to press Post more than once. If you've pressed it, it will post.
If anyone is still finding something to be very slow, please let me know your location, type of Internet (dial-up, DSL, etc.), browser and operating system. Thanks!