Landscape Always Asks for Lighting Build

I created a landscape of 32x32 (=1024) tiles, set a material for it, textured, sculpted a bit. Than I decided that I want to see how it actually looks(because top left corner says LIGHTING NEEDS TO BE REBUILT (1024 unbuilt object(s)). I click on the Build button on the panel. It just builds, than says that the lighting build is completed and I click on Apply Now. And I expect the lighting build to be done, have some lightmap visible in action, the preview text removed from shadows etc. But nope - nothing changes. And the left corner just again says that I need to rebuild lighting. I tried building a few times, but it just keeps saying that I must rebuild. I got annoyed and came here to ask. So how do I build it so that it doesn’t keep me asking for build?