Ooo I'm definitely adding sauerkraut juice to my next batch, I use avocado oil and immersion blender as well! You can add a Tblsp of whey as a preservative it will last a few more weeks, but as you say, the scavengers always get it before it's too late!
The sauerkraut juice is also supposed to act as a preservative, although I kind of question whether it would be as effective as the whey.
Darn scavengers! Good thing they're cute!!