Is there a way to download and store Google Maps permanently?
I use MAPS.ME as an alternative. It works perfectly offline, you can save places, search anything in the downloaded maps, and it has a router for driving and walking too. Its map data is from OSM. It is also accurate enough, (but) it can be edited by anyone, though this can lead to mistakes (I've not encountered any of them so far), and on the other hand, sometimes it is even more detailed than Google Maps.

Anyway there are a lot of apps on Google Play using OSM's data.