How long should batteries last on 2-battery Apple bluetooth wireless keyboard?

How long should batteries actually last on the 2-battery Apple wireless keyboard (without a trackpad or Magic Mouse)?

I purchased one a couple of years ago to use exclusively with a 2008 Macbook running OSX 10.6, with probably 8 hours a day of active use. For a long time I didn't have to change the AA batteries for months. But three months ago it started needing a battery change once a month, and now it seems to have died, so I need a new keyboard. (When I insert new batteries now, it powers on for two seconds, then shuts off. I've tried cleaning the ends, using tinfoil as a conductor, etc., but nothing helps, so I'm resigned to buying a new keyboard.)

I've been trying out a Logitech Solar Keyboard for Mac. It's cheaper than the Apple, I love knowing that I won't have to change the batteries, and the keyboard action is similar to the Apple (a bit "clickier"). But the connection fails a couple of times a day (the Apple wireless rarely failed) and the keyboard is totally flat, i.e., not ergonomic--not a deal-breaker, but annoying.

I'm considering returning it and getting another Apple keyboard, but I've been reading a lot about people having to change the batteries once every two weeks--and considering that "good"! That seems ridiculously frequent.

Can anyone who's been using just the Apple Wireless keyboard (no trackpad, no Magic Mouse) for, say, a year tell me how often they have to change the batteries?

And if anyone out there from Apple is reading this, how about considering a solar version of the non-extended Bluetooth keyboard, and giving us Macheads the best of both worlds? For a price, of course....