I attempted last night to let the build process wind out on a large, single NavMeshBounds object. The size of this object was 40000 x 50000 x 10000. I began the build process Just before I went to sleep, and it very quickly went to (“Building Navigation (12)”) before freezing. I then left the process running all night while I slept, nearly nine hours. When I woke up, the editor was still frozen with the log displaying (“Building Navigation (12)”).
After that, I must deem that building from a single NavMeshBounds object is impossible (or just unacceptable?) for this level. I can’t just let my computer process that for two days each time I make a change, or however long it might take (assuming it would finish the build process at all).