rundmcarlson :
The square mileage depends on the map density. You aren't going to get 200 square miles (or even 20) of NYC or LA or any other major city. 200 square miles of montana isn't an issue.
I'd be happier if Google Maps dynamically saved maps in areas you're traveling through. That is, they add a setting which lets you save, say, up to 100 MB of map data. Whenever you use Maps, the last 100 MB of Map data is stored on the device. If you enter a new area, that data gets downloaded and saved, and pushes the oldest saved area out of storage.
Several times I've been using Maps to navigate and it crashes (display locks up). I'm forced to reboot my phone, I start up Maps again and... I'm in an area with poor cellular coverage so it takes several minutes to re-download the map of the area I was just in. So I have to pull the car over to the side of the road (since I don't know where I'm supposed to go), and wait several minutes for Maps to finish downloading before it can resume navigation. Whereas it already had the map data and route prior to the reboot.
To me that's a more common issue than wanting to pre-save maps because I know I'm going to be hiking somewhere where there's no cellular data coverage. Best would be if they could combine the two. So I could designate an area as always-save. It will download and save the maps for that area. If it has a data connection while navigating, it will check that area's maps for updates and download as necessary. But if there's no data connection (or it's limited), it will rely on the saved maps for navigation instead of waiting for an update before telling me where to go.