I've gone 2 weeks in mine without problem. I got stuck in Greece in May thanks to Mr. COVID, and was gone 25 days. Battery was dead when I got back.

I've got a tender, but was only supposed to be gone 2 weeks so didn't put it on....

 

The battery drain problem is most likely traceable to bad capacitors in the audio/radio system. That is why it seems to be random. If you disconnect the radio/audio system and the problem goes away, you have found the culprit. I have a 2004 LS and a 2006 SC neither have that problem with fresh batteries in them.