Alright, so as the resdient only-person-who'd-ever-think-it's-a-good-idea-to-install-offline-routing-maps-for-the-whole-world, I can confirm that cramming your N900 with hundreds of different routing maps isn't the most optimal thing to do for performance (more so than it probably has to be). Now, I haven't tested actual routing much yet (was very glad to see the new version in the Devel repos though, with offline address search as I understand it) but the more I've installed the more abysmally slow Marble's MoNav configure menu has gotten. (Marble itself is a bit more memory intensive now but isn't actually slow yet, at least for map display - I haven't tested routing in a while.)

Now, that's obviously logically sound - it has more files to check/verify for map updates, etc. However, it is insanely memory hog-ish - to the point where with Marble running by itself (not actively installing a map, just on the MoNav configuration menu, usually after having installed a new map), causes out-of-memory errors - I.E. you go to launch Conversations and it tells you there's not enough memory and you should close some applications (I've only ever had this happen when I turned swap off once), and doesn't launch conversations.

This leads me to believe that Marble/MoNav keeps more data than necessary cached at once when checking for updates and/or installing maps (the entire map list, with all the versions/relevant data?). Wouldn't it be possible to load part of the map list, check it against the server, keep in memory only the data for maps that need updating, and then free the memory of the rest of that part of the map list, then load the next part, etc?

I'm going to keep reporting my experiences here - while this isn't a common use-case, I think me installing every single MoNav routing map on my N900 would be useful for seeing how Marble handles that extreme of things.