...and frequently polling the GPS receiver will quickly kill your battery.
...as will frequently polling for WiFi.
Install some toggle widgets for them on your homescreen. I find they are quite convenient. Switch WiFi on when you're downtown, on foot, or in office buildings. Everywhere you may expect a high density of WiFi hotspots. Switch GPS on only when you really
need navigating. They'll give you high resolution services, and drain your battery fast.
That's not a problem at home, in your car, or in your office, because a charger is usually near.
But if you have no live charger available energy consumption becomes an issue, like it or not. Meaning you can't afford to waste it. You need to conserve it for when you
really need it. Depending on the circumstances, of course.
Besides switching GPS locating and WiFi polling off (with widgets) when they are not necessary or useless (like GPS in buildings, or WiFi out of town) I now also kill all apps about twice a day with 'Advanced Task Killer' (in the market). I know many of them come back on automatically within minutes, but I also find empirically that this 'energy husbandry' effectively at least
doubles my battery life!