cldisme:"permanent Lego-built items"
Sounds like an oxymoron to me.
As for the concept, how many are out there that are not part of a LEGO store - which failed in Peer Review
http://www.waymarking.com/groups/details.aspx?f=1&guid=d748f6c6-2349-422f-a5ff-21964c560725
They're permanent if they're no longer able to be disassembled into usable LEGO blocks.
As in glued together and stuff.
Even if they're on the grounds of a LEGO store, we ought to consider that permanent, as we waymark lots of stores as if they're permanent.
So there'll be stores, LEGOLAND, Discovery Centers, and the occasional other one like at the airport Bruce mentioned.
Perhaps they need their own category?