I made a blinking marker light with an LM3909 and an ultrabright red LED running off a D battery about four years ago. It blinks about once a second, and is still going. If you can deal with a blinking light (maybe add a switch to make it continuous for reading, etc), you can really extend battery life. Of course, the '3909 isn't in production anymore, but there are some simple transistor ckts which do the same thing.
Off topic, there are also those small trituim-filled markers you can find on ebay. Those things aren't very bright, but they essentially glow forever, losing 1/2 their brightness every 12 years or so....