|I'll take a translation if someone has it.
Ah, war story time. I'm only including it here for background. I'll try to be brief.
Some readers might remember one of my parties is in possession of a flying ship. Saturday, this led them to a floating town in the sky, Ternketh, a collection of wattle-and-daub houses, a group of some hundred 'docks' supported by nothing at all except magic, surrounding a castle-keep. The entity is about a mile in diameter and largely denuded of people, as some years ago Ternketh was attacked by 80-200 harpies. Most of these harpies are gone now but the remainder dwell in the keep and are kept away from the still inhabited part of the town through the use of wards (an occasional person is still caught and eaten).
It isn't known how many harpies are left - probably more than ten, perhaps as many as fifty. The party also learned that the wealth of Ternketh - so far as the town knows - remains in the keep, as none of the Lords there were able to get free. All were charmed and destroyed. A view of the keep 'yard' (made of stone) from the air showed large patches of dried blood and many bones.
There, those are the details I'll render; the party hasn't actually entered the keep yet, so I can't say more than what the party knows. If someone wants more information, I'll share it but only so long as it's something I've already told the party (or might tell them, since after reading a question here they will probably ask it during the next game anyway).
My point for writing the post is this: the party had most of the information they really needed by 9 o'clock. There were details to be worked out, obviously, but by nine they had decided to go in and do their best. They're 5th-8th level, most of them have wicked saving throw bonuses on account of various benefits, they've loaded up with one heroism & one speed potion (they're going in at night), an ultravision scroll and there are 18 total characters, henchmen and followers involved. They have waxed their ears to stop from hearing the singing and they're loaded for bear.
We did not run any combat Saturday. The players spent two hours planning and I called the game at eleven.
I have watched this phenomenon again and again. An unknown number of harpies is concerning. No one wants to tackle that - but they don't want to lose out on heaps of treasure, either. Understandably, they want to be sure they've covered everything. They've got a lot of manpower to share around and naturally this has to be done right. There's every chance the wax won't work - that has to be considered and a ready plan for that contingency is in the offing. The players are wise enough not to rush when they could better prepare themselves.
And yet . . . two hours. I wasn't bored. The players weren't bored. There was plenty of tension and voices were rising a bit here and there.
None of the adventure is quest-driven. The party is on a quest, but they have a little time to spare and this is very tempting. But they know they can back off and just continue on their way (though it is guessed already that the harpies know something is up, since the party passed over the keep in the daytime in a big floating ship, and may choose to swarm the ship as it leaves if they believe the ship's owners are frightened and weak). They don't have to attack the keep. They're not terribly concerned about the townspeople but they won't mind saving them anyway, since there's at least one old man (a venerable cleric) who might be a very good friend to the party.
Players will, however, find excuses not to go right now. As a DM, it's important not to push them. If they want to spend the rest of the night going back and forth over the best tactics, for the love of blue bloody bacchanalian behemoths, LET THEM. The game is running itself. A resolution will come in its own good time.
A forgivable error - but an error, nonetheless - comes when the DM mistakes 'pacing' for 'advancement.' Though the party may not be taking physical action or physically moving forward as characters, this does not mean there is no momentum in the game. Some momentum is oscillation; where the same ground is gone over and over again because the players are adapting themselves to several things that may be about to happen due to their decisions: one of them may die; something dear and important may be lost; there may be other unforeseen consequences that could have been avoided but are now part of a reckoning.
The unknown is concerning. Whenever possible, let the players make up their mind about how concerned they want to be and then wait. Just wait. As I've said many times, these moments are not about the DM. It's about them.