Here is a good way to actually locate the problem and fix it. Get a test light, disconnect your positive cable and hold the test light between the cable and battery. If there is any drain (which there has to be for the battery to die in a couple days), the light will come on. Have a friend help you and start pulling one fuse at a time until the light goes off (test light). Once you find the circuit with the problem you can repair it. My car can sit for weeks and the battery doesn't go dead. I have seen bad flashers cause this problem, also "disconnected" dome lights (thought to be disconnected but actually were shorting). It might take a little time to find the problem but, it will be worth the effort. Yes, stereo memory does require some current (very very little), if you have a cd changer, some of them use a bit of power if you leave the magazine installed.
Make sure you battery is holding a full charge to start with and that your charging system is doing it's job (car running you should have at least 14.4 volts). Fully charged battery should be around 12.5 - 13.0 volts. Make sure you have a good clean ground, from the battery to the frame or engine and from the engine to the frame. Most people overlook the ground as a problem. Just say to yourself "electrical problems are fun", LOL. They really aren't that bad, just be patient.
