On H:LOTS, I can kind of see stalling a bit on that in Season 3, as that's where they first start getting a lot of cast changes. Also, the last few seasons are overall much weaker then the first two -- but if you can slog away at it when you're in the right mood, even the weakest final season still has some good moments! Also the cast changes after Season 4 bring in a few more female characters, and while none of them are quite as awesome IMO as the utterly fabulous Kay Howard, they still have some pretty good moments as well -- I always particularly liked Michelle Forbes' character, the new M.E. who shows up in S4.

I'm not sure about the Tibetan and Inuit influences, though I have a lot of faith in the writers.

The Southern and Northern Water Tribes appear to be a bit of a blend of elements from various different Arctic and sub-Arctic native peoples; the Inuit elements seem the most prominent, but the totem-pole-like ice sculptures in the north looked like they were based on the art of Pacific Northwest nations like the Haida and Tlingit, and their riding-reindeer/goat creatures bring to mind the taiga reindeer domesticated as draft animals by the Evenk and Even people of Siberia...and Sokka's ball-headed club actually resembles some Plains and Eastern Woodlands weapons. The protective eyewear everyone whips out in "The Eclipse" looks like it was modeled directly after Inuit snow goggles, though!