To add a question to this discussion. I recently topped off my DEF tank for the first time. Truck had ~ 1000 miles on it, so it didn't come with a full tank. ( I was pleased enough it came with a full tank of diesel, given the price of the stuff ! )
It was getting close to the "red" zone on the gauge and I was about to head out on camping trip into the mountains and wasn't sure what range I had left ( side question, is there anywhere in the various info screens on the truck it gives you estimated DEF range left ? I haven't seen one but may have missed it ). I know from the manual there's a warning when it gets down to some level, I'm forgetting what that is right now.
Anyway, I bought 2 jugs of Platinum and poured all of one into it, and about half of the second one.
I'm thinking it'll be a good while before I need to add more as I don't do a whole lot of driving in the truck. Will this opened jug last a while ( months ? a year ? ) or should I just throw it out ? If so, where? On the manure pile ( I have some animals, and DEF is mostly Urea + DI water I believe, so seems like it might be just fine on the manure pile

)