They tend to be a lot shorter in newer shows though. Older shows' credit sequence would typically last over a minute, whereas IME they tend to be 30 seconds or less on newer shows, some even less, and some only have a title card sting.
If there is any correlation I've observed, it's more to do with the genre of show and it's running time.
Take Boardwalk Empire, another really long intro. Yet Lost, which is an older show, only had a title graphic that lasted a couple of seconds.
Not just that, but the images in each region are subtly altered to reflect the events in the storyline in that region.