It would have a lot lot better feature if Android could manage battery usage for things like GPS in a low power mode[1] even if it was on all the time and would only activate in the background intermittently or AGPS fetches some region of interest. Though for this to work efficiently AGPS shall have to be more accurate than it is as of now - at least available on Android phones.

[1]Sth like Bluetooth Low Energy (it requires additional h/w though)