I'm planning on migrating the forums to a new software within the coming months to Discourse ( https://www.discourse.org/ ), which is a bit more modern and lightweight. The current forum software is overkill for what we use it for (nothing) and they negatively changed their licensing model a while back.
With the migration most things (forums, topics, posts, and most users) will migrate automatically. Some things, however, will likely be dropped or not convert exactly the same way so you may want to backup anything below that is important to you:
User avatars don't migrate
User profile backgrounds don't migrate
Signatures don't migrate
PM/DMs don't migrate
Passwords have to be reset
Accounts using Steam login will likely have issues
No public facing shoutbox. There is another real-time chat system built in, only for logged in users.
The calendar/event won't automatically have it's own section. There will be a manual replacement though.
I'll also be purging some stuff along the way including but not limited to:
Any accounts with 0 posts.
Dropping the News section with auto-created posts from TTK bot
Dropping the Archive section