dead battery

My '95 Yukon XL has super low miles & is in excellent shape, except the brand-new battery keeps going dead on me. Have had it towed to multiple shops. They say the alternator is in great shape. We've cut off all superfluous electricity drainers, like car phone & vanlty mirror lights. The latest...

204 gmc sierra sle ext cab 5.3ltr 4wd.i used the test light from the battry post to the battery cable and it shows a drain.why wont the test light go out when i remove each fuse one at a time.shouldnt that isolate the bad circut?so i could chase it from there.did the fuse remove thing on both...