Aftermarket was a X2Power, 840CCA, and 76AH and it lasted approx 6-mo before showing low charge and then no charge. As of yesterday, dealership says this battery will not hold a charge and has to be replaced before diagnostic testing can be done. Have to believe there isn't a parasitic draw ...
Your original post said 775cca, I’m not seeing a 840 with 76ah but could be wrong. No matter the size of the battery these trucks are hard on batteries and driving habits will be a factor. Even with a large battery I place it on a trickle charger periodically, it’s actually good for the battery to get a full charge sometimes (the trucks won’t fully charge a battery).
I’d still bet getting the battery I listed will solve your issues. A battery lasting 6 months before showing low charge doesn’t seem like parasitic draw…
Another thing to look at, where are you keeping your key fob at night? Anywhere close to the truck? If the truck can detect it slightly, it will never power down.