I find it unlikely that some defect outside of the battery and alternator caused both to go bad twice. You may be just that random unicorn that happens along every so often. I had a 1986 Tempo that had three shorted batteries in a row. How can I say this right? They all gave 100% service between bouts. You would be going along for weeks or days and all of a sudden you would have the dash go crazy and no start. Replace the battery …fine for months …same deal. The 4th battery solved the issue. …oh, yeah, the left head light would burn out shortly before the battery shorting out. Yes, it sure sounds like I spotted BIG FOOT and a herd of unicorns.
What I think the other poster means by “dark load” is one present after the engine is off.