Just my $0.02

Does this car have a replaced wiring harness?

It would seem to me that an intermittent short may discharge a battery, but, unless you have fixed the problem, it very well may just come back when the wiring moves again - at which point, you'll be deep-cycling the battery again. It certainly sounds like the easy starting right now is a byproduct of having a brand new, fresh battery.

My battery is at 12.49V when off, and 14.10V at idle.

If you have a small current leak, you might not see it directly at the battery in terms of voltage. Perhaps closer inspection of the fuses may help you isolate where it might be. OTOH, maybe your leak is large enough to be more obvious.

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1982 240D, sold 9/17/2008
1987 300D TurboW124.133 - 603.960, 722.317 - Smoke Silver Metallic / Medium Red (702/177), acquired 8/15/2009
262,715 and counting