That could explain it, I never let mine go online except for when activating or just checking the hybridl maps for fun (that's nothing to do with agps and network positioning). Might be beneficial, but since there's no traffic info here and I don't really use the hybrid maps, I don't really care about it (maybe there's more to it than this).
I've just tested the navigation for about 45mins and didn't have any problems, but that's a short test.