My group is currently running kingmaker. As a way to augment the story, we have been looking for and playing other river kingdoms adventures. Along those lines, we picked up the Emerald spire super dungeon because it took place in the echo wood. A couple of questions we had that we were hoping someone on the forums here could answer:
First, can the adventure be broken up piecemeal? That is to say, could we run part of it, go do something else, and then come back or is it really meant to be run start to finish with no interruption?
Second, about how long does it take to run the adventure?
I've run (not played) the first ten levels of Emerald Spire, and it's been enjoyable for the group. Each level is relatively independent of the others, though they are loosely tied together by the overall story, but this can be ignored without detracting from the experience.
One thing I would suggest, since it is a superdungeon and space is at a premium, is to not build characters that will clog up the map with figures. It will get cramped.
I have run 1-15 so far in PFS. Some floors are very fun. Some are slogs that don't meaningfully contribute to the overall story. Because you're looking to insert bits and pieces, you can certainly just write out the floors you don't want to do or leave them and say that they've been cleared out by other adventurers.
As Chess said, each floor takes a while. They typically can fit in a 4-5 hour PFS slot. Essentially, if you want to clear a floor, plan a session around it.
One critical item of note: some floors are VERY low loot as written. GMs who insert floors should definitely consider adding items or modifying the contents to fit the campaign. Additionally, it's worth considering whether Fort Inevitable plays a part, because there are some special considerations if it's included.
Nothing has been decided, of course, but a suggested hook was that the fledgling Kingmaker kingdom, in need of resources and some advantages, would hear about the Emerald Spire and dispatch a group to wrest some profit from it. The Emerald Spire narrative would be mainly its own thing, only tying back into Kingmaker in the form of the participating characters, any recovered loot, and how the Spire narrative affects the River Kingdoms at all.