My PCs have always had pauses, either because I like sending them all over the world or because they stop in cities, get the hang of it, wait to talk with important people, spend some time on having fun like carousing in taverns and so on...
I also plan for story arcs in my campaigns and between a story arc and the next a few years of game time may elapse (as well as a few months or real life time, often, taking breaks and playing other games).
That said, advancement tied to adventures has always felt unrealistic to me, and more so in D&D as it's a level-based game where you start as an incompetent (remember the old saying "a cat does more damage than a first-level mage"?) and then push beyond normal human limits.
In the last few years I stopped bothering calculating XP; I keep all the PCs at the same rate and they level when it feels right in the story for them to do so. My campaigns aren't filled with combat anyway - there is action, but I tend to stage few, significant encounters.
For instance, in the WoW RPG campaign we were playing until a couple weeks ago (time for some Witchcraft goodness right now) my PCs travelled from Theramore to Bael Modan, where they discovered - or rather, were ambushed by - a fairly unknown (they're Alliance) race of pig-men, they investigated the burned inn, had some troubled daily hunting (1), met with some Horde folks and managed to talk their way into getting help with the investigation, then - thanks to the shaman's prophetic dream - saved a dwarven caravan from dragonkin magically disguised as orcs, and last but not least got to talk about these grave matters with Lady Jaina Proudmoore herself (2).
This was worth a level, the meeting with Jaina being worth as many XP as the dragonkin fight (yes, they had help, but I had factored this when planning the encounter, so they faced more than they would have on their own).
As for game time involved, the above took about 1 full month of game time, what with travelling on foot back and forth and so on; and about 5-6 evenings of real time, so that's slower than usual (but we play less than 3 hours an evening), I wasn't using the book rules anyway, and my players are fine with my story-driven pace, so we're all happy.
From what I've heard the new rules for XP are largely similar to what I'm doing now, and of course this makes me happy.
(1) the group hunter felt too merciful to kill rabbits, and tried to get a boar instead. A long and comical fight ensued (yes, can't wait to see some justice to ranged fighters) - and in the end they had rabbit soup for dinner. Yes, I'm evil.
(2) for the one reader who might not know of this, Jaina is a world leader.