Basically to preserve battery, it's best to use the compass all the time.
That'll help, I usually have the maps on display with the screen brightness turn off, as I can be a little paranoid about missing a turn on a route I don't really know.
Well I presume it's still going to use the GPS to know where you are so that it can point the arrow at the next place. Otherwise it's going to be hard to navigate anything that isn't a long straight line.
Basically to preserve battery, it's best to use the compass all the time.
That'll help, I usually have the maps on display with the screen brightness turn off, as I can be a little paranoid about missing a turn on a route I don't really know.