Comment by Retric

Try zooming in on Russia, Alaska, Brazil, or Egypt and you find a lot of empty tiles. Still, if you can render the whole thing in 4 days I suspect caching what people actually look for would be good enough as people probably hit max zoom on manhattan 1000x as much as they do on some random village in the amazon. The advantage being you can just invalidate tiles as you get new information vs trying to render the whole thing every time you get new street data for Ohio.