2002 Subaru Forester Battery running flat

Even with regular use my battery is running flat ever 3 weeks or so. I have had it jump started by my road side assistance provider about 4 times and they tell me to give the battery a good charge as something seems to be running it flat even though the battery is one year old. So I have been trying to find a cause. What I believe it to be, is the power window illumination lights, that seem to be staying on after the car is locked and every other light goes out. Subaru can't/won't tell me if this is common, or how to fix it without taking it in so they can ponder the possibilities for hours and charge the GDP of a small nation. So, I'm hoping you have seen this before and have a suggestion. I've trawled thru the posts and haven't stumbled on anything similar.
Thanks and regards,
Chris Whalen