I usually render at 2000 - 2400 wide and use custom settings, and rarely go over 10 hrs. of render time.
Renders of 20 - 30 hours or more are usually the results of lacking skills/knowledge, unless they are HUGE.
About Drea's render mentioned above, it shouldn't take that long. Sure, there are some low density clouds, which is notorious for producing heavy renders, but still... I've also noted that she often uses the Vue presets, e.g. the "Broadcast" mode, that's not particularly clever. She may be one of the most popular Vue artists, but certainly not among the most skillful. An example of a skillful and great Vue artist: Artur Rosa. That's a whole different league IMHO.