Short stories should begin at the last possible moment that still allows them to be a story with a beginning, a middle, and an end. They should begin with an inciting incident. Break this rule if you want, but do it cleverly, or you're done.
With novels, you can actually screw around for a page or two before the inciting incident, but that's only because in a novel the people you are with are sometimes more important than the inciting incident. Maybe seeing a character clearly as they do something mundane in a quite non-mundane way is worth some pages. Even a frickin' chapter. Obviously, the non-mundane mundanity should lead us to the inciting incident, so we've got time. To be safe, though, the novel should kick us right away too, in the first line, again in the first paragraph, and again in the first page, giving us something interesting and entertaining and intriguing and continuing to kick us all the way through the whole damn book.
Don't get me wrong: You can be slow and pastoral, that's fine, you just have to be slow and pastoral in a way that kicks us and keeps on kicking us.
Not that it's ever okay to take a break and be boring. It's really never okay. I just read "Magic's Pawn" by Mercedes Lackey, and in addition to the near constant exposition by dialogue (the entire book is composed of it), the fan-fiction Mary-Sue wish-fullfillment, the constant stream of unexplored magic-thrown-in-just-to-be-cool, and the fact that there really isn't any kind of plot other than "whiny boy gets hurt a lot and whines", there are long passages that are exceptionally boring.
You know what? Everything is forgivable, except 'boring'. Seriously, I've read descriptions of gardens that stretched for pages and loved them, I thought Moby Dick was wonderful, and if you start fulfilling all my fantasy wishes in your mediocre writing, I can forgive it. Go ahead and have some characters be randomly telepathic just so you can continue your exposition-by-dialogue and never actually have the characters reveal their emotions through action. Fine. Jerk. But I'll forgive you. Just don't be boring.
Then why did I finish reading "Magic's Pawn," and why did it get published at all? Probably because it begins very well. Oh, the first few pages are crap, but they lead right into an inciting incident and a whiny main character who is actually trying to do something about his situation. The first several chapters are really quite good, in a "standard fantasy hero" kind of way. And then, not long after the "hero's journey" begins, you meet the author's cipher, drawn loose and shallow with all kinds of intense emotions that are somehow utterly boring, and the poor qualities of the text just leach away any potential the book may have had. It's fan fiction. We are supposed to admire and want-to-be this character, who is the "hero's teacher" by the way, and instead she's like Jar Jar Binks... as soon as you realize that she's going to be central to the narrative, you know you are screwed.
Everything that happens in "Magic's Pawn" happens just so the main character can have a lesson. Everyone arrives when they are supposed to arrive. We have all these convenient bits of magic and all these convenient plot items, and then none of them seem to really matter to the author. This is a lot like reading about the main character's career or hobbies inside a romance novel... good background noise, sometimes, but often irrelevant. The difference is, in a romance novel you can actually care about the romance. The relationship itself is the main character, and you can forgive the other plot items for being irrelevant. (A really skilled romance author, of course, makes the background noise sing.) That kind of "I'll forgive you," never happens in Magic's Pawn, even though I kept expecting it to, kept reading, hoping that it would. The result is that everything in the novel is background noise.
Anyway: don't be boring.
In retaliation, I need to read something good. I am open to suggestions. I just grabbed "Never Let Me Go" for twenty-five cents. It was all "Look at me, I'm a Booker Prize finalist! And you loved Remains of the Day!"