I don't know enough about vBulletin to know if this is possible, but is it possible to show the date a thread was started (i.e. the date of the first post in the thread) while in one of the indexes? Sometimes old threads get bumped to the front and if you click to read the thread you don't immediately realise that it is old content.

Some forums do this by showing the date on the index screen either all the time, or when you hover over the thread link.