Sara Mae Highfield

Okay so I don’t know anything about vehicles just looking for advice. I have a 05 Chevy Tahoe z71 with 200,000 miles. In the last 6 months it’s been in the shop more than not and when it’s not in the shop it won’t start. Nobody can find the problem. I’ve had 3 different brand new battery’s on it and 4  alternators. In 6 months. It also has a new instrument cluster that was put in about a month ago.  With a lot more things done. I’m just not sure what. I just know it’s been expensive. But still if I leave it sitting for more than an hour or two, the battery is dead and I have to jump it off. I’ve learned that if I unhook the battery cable, it will last for around 12 hours but after that. Dead. The  mechanic said there was a short because sometimes all the interior lights won’t come on, only the front and very back, the middle won’t come on or if you open a certain door none of the lights come on... but still the problem can’t be found. Any advice on what to suggest to look for? I’ve had it almost 4 years and it’s been a good vehicle until this happened! Please help!