I don't need nearly that much. I generally download only one zoom level, maybe 2. One level for normal tracking, and maybe one big enough to see the whole route at one time. I see no need to have all zoom levels, or even half, for an entire area, or even one state.

I do have the entire US, all zoom levels, on one 1GB SD card, using vector maps, though. There are reasons vector maps are much better - size and autorouting capability being two. They aren't as pretty, though, nor as cheap. I don't bother with the basic VE maps, just the hybrids, so I can view the photos. For actual driving directions, I have a vector-based program on a Palm and a standalone GPS. MM on a Nokia is just for fun, and I would never tie up terabytes of storage for maps for it.