For Lego Space builders there's a tradition: SHIPtember. Each September, any Lego fan can try to build a SHIP. (Also known as a Seriously Huge Investment in Parts). It's typically for spaceships, but I think landships work just fine. Minimum length of 100 studs, preferably to be built in a single month.
Khagaan took three. The two smaller vehicles took a month each. Now I've finally finished filming and editing, it's Shiptember again. So in that way, it's perfectly on time :)