Arravis said:
I disagree that it's very little gain... the gain is enormous. And once you're 18th+ lvl, the resources to pull this off aren't that much. Spend a month or so using divinitions to find the proper plane, then move in and summon creatures to create an abode, or use a Daern's Instant Fortress created with a lab.
If it could be done with a month's worth of divinations, then it would have been done so, many times. The results would have become common knowledge (at least common among wizards), and the divinations would not be necessary.
Plus, a month of divinations? What divinations would reliably give the information? Legend Lore and Vision don't generally give detailed information (I'd consider the exact compositin of the Plane Shift fork to be detailed), and what you know about the plane is certainly "rumor". Contact Other Plane might work - but it'd take *lots* of work (one word answers!), there's a risk in each casting, and the powers of other planes (read as "the DM") may not want mortals plane-hopping around to do such things.
Summon a creature workforce? The monster summonings have durations in rounds. You can extend that, but then you're requiring an extra feat. Planar bindings are risky. Planar Ally requires you be a cleric. Neither one gets you all that many servants, and who says that summoned creatures are skilled at construction? Sure, they'll build it, but it'll fall down!
The Instant Fortress isn't a bad idea. But, it isnb't exactly a minor item, now is it?
All this, and if he doesn't have the requisite XP on hand when he wants to create the item, it all goes for nothing? *shrug*