I shall be closing the site for a few hours tomorrow morning (3 February 2012) for some overdue maintenance.
I've taken the day off work to focus on the activity. If the upgrades go well then it should only take a few hours however it could take longer if there are problems.
As always I'll do a full database back up before starting work but if you are worried then please save any important posts, messages or files you have here.
Any questions just ask.