Left town on Saturday and wife calls me on Sunday saying she tried to start the SRT8 but the battery was dead. I got back Sunday afternoon and there was just enough juice in the battery to make the instrument panel lights flicker - not even a dome light. Put the charger on it for 10 hours overnight and in the morning the starter was barely able to crank the engine over, but it did start. Since it was started I ran it over to the dealer. They measured an 800 milliamp draw on the battery with the ignition off, but it went away after they opened and closed all the doors. The service manager speculates that it might have been a door switch stuck - but not enough to engage the dome light. Sounds quite speculative....
Anyway, their check on the battery indicated no problem there, I drove off...
jmk, I'm like you; the factory battery never seems to last very long. Usually less than 2 years. My one exception was my '96 Ford Windstar, that one lasted 9 years, and almost 2 months. When I had to replace the battery and the alternator.