Most films have a Title and Credits. We have all seen extreme examples of the legibility and length. From less than 1 second long exposure of the 'best boy' name as it scrolls in small font up the screen (along with lots of other names); to the Producer's name which might appear for an eternity (perhaps visible for up to 10 seconds). Understandably, some editors may pander to their clients or boost their egos etc.
If the message is simple; and the text is displayed in an easily readable font; then how long a display is necessary? At the moment, I am judging around 2 secs might be reasonable for a simple credit, such as "Narrated by Tim Andrews".
But - does anyone have a rule of thumb which they use when setting the length?