my old 94 burb would have a low battery daily for a while but would start if I started it the next day.... So one night forget why I was in the truck and noticed the light up in the passenger side sun visor mirror was on.... adjusted the viser so it hit the button properly and bamn... nailed it. check that out because I was getting really frustrated not being able to figure out why...
YUP, that happened to my 99 burb. The little tab that holds the plunger switch in had broken off both of the visors, And the dang bulbs do not come out. I had to take the visor mount, trim shroud, and headliner loose at the "A" pillar and unplug them. This went on for a month or more for me AND the guy I bought it from. Yeah, I bought it from a friend.
I finally noticed llight leaking out from behind the mirror one dark night. I have to keep the dome light override on DARK because the plunger switch on the driver's door is broken, and I haven't gotten around to fixing all the small stuff yet.
Another thing someone hinted at that might be a problem; After I drive for 1/2 hour or more, and try to start it again before it cools off, it acts like the battery is really low, but what it is, about every month or so, I have to go in and wire (steel) brush both battery cable ends and the battery terminals. It's those d#% side post batteries. The tiniest bit of oxidation and the connection goes south, especially after the engine bay gets hot.