Why won't car start?

What is your question?

My husband's man cave, uh I mean used car (2004 Cadillac DeVille), which he has had for two years, has been refusing to start on an intermittent basis. It might start in the morning and then we'll go somewhere later in the day and it won't start. His battery is about a year old and he's had it to three car repair places. One was a dealership and the other two were respected car repair establishments. So far, they've replaced the alternator and tried to analyze the problem on their computer equipment. He also replaced a part that was effecting how the driver's window worked. Since his retirement he doesn't drive as much, so he often sits and reads in his car so he can smoke his cigars. Once this problem started he has made sure to run the car each day and to shut off everything before he leaves. He turns off radio, heat/cool, etc., so that none of these taxes the electrical system when he goes to start it. We researched the problem on the 'net and even have tried starting it in neutral. We purchased a Stanley 1000 Peak Amp Jump Starter, which worked well the first time we used it, so we could avoid called AAA or friends. Now, it doesn't start the car. Please help us find out what's drawing his electricity and causing the car not to start. Because of his height, my husband has a hard time finding a used car and he had hoped that this would be his last car.