I currently have Fedora 14 and the battery life is not so good. I am planning to switch to Fedora 16. Will I get significantly more battery life if I go for the LXDE spin instead of GNOME?
I doubt that LXDE vs GNOME will make a significant difference, but I don't have hard figures. I doubt less that the default configuration of LXDE and the default configuration of GNOME will make some difference. To keep power consumption down, turn off desktop effects (animations, anything 3D).
Make sure you're not running any kind of “screen saver”. Most screensavers are demonstrations of advanced video capabilities; they're huge battery drains. Make your screen go blank when you're not using it, and make sure the video card isn't forever refreshing some picture in the background.
Run PowerTOP to get an idea of what's using power on your system.
you could try the jupiter applet, its a power management applet for laptops and netbooks, very very handy to get longer battery life,i use it in ubuntu, but its also meant to be supported in Fedora 14, have a look here http://www.fewt.com/2011/01/jupiter-applet-gets-its-own-home.html
If you are interested in improving battery life, then you should sure try jupiter (although the sources to be compiled). The basic documentation is available at http://sourceforge.net/apps/mediawiki/jupiter/index.php?title=About